US3524777A - Slurry explosive containing an improved thickening agent - Google Patents

Description

United States Patent 3,524,777 SLURRY EXPLOSIVE CONTAINING AN I1VIPROVED THICKENING AGENT Yoshikazu Wakazono, Kyoto, and Yoshiyasu Otsuka, Niihama-shi, Japan, assignors to Sumitomo Chemical Co., Ltd., Osaka, Japan No Drawing. Filed June 5, 1969, Ser. No. 830,868 Claims priority, application Japan, June 10, 1968, 43/42,648 Int. Cl. C06b 1/00, 7/00, 9/00 US. Cl. 149-41 6 Claims ABSTRACT OF THE DISCLOSURE A slurry explosive comprising a composition consisting essentially of ammonium nitrate, or a mixture of ammonium nitrate and an alkali metal nitrate, or a mixture of ammonium nitrate and an alkaline earth metal nitrate, or a mixture'of ammonium nitrate and an alkali metal nitrate and an alkaline earth metal nitrate, at least one member selected from the group consisting of 2,4,6-trinitrotoluene, aluminum, smokeless powder and fuels, and water, 0.1 to 2.0% guar gum, not more than 0.3% of a borate or borates, and/or not more than 20% of hexamethylene tetramine, and 0.02 to 2.0% of an antimony compound or compounds, all percents being by Weight.

BACKGROUND OF THE INVENTION Field of the invention The present invention relates a a slurry explosive having stable physical properties. More particularly, the present invention relates to an improvement in a thickening agent which, blended with a slurry explosive, maintains it in a uniform and stable state as a good suspended dispersion condition over a long period of time.

Description of the prior art The slurry explosive obtained by blending as the main ingredients ammonium nitrate, or ammonium nitrate and an alkali and/or alkaline earth metal nitrate, 2,4,6-trinitrotoluene (hereinafter referred to as TNT) and/or aluminum, or their mixtures, and water in a pasty state is well known as an industrial explosive, and has been used in places such as hard rocks or water springs where an ammonium nitrate-fuel oil explosive cannot be employed. In addition, this slurry explosive is very safe in handling and easy to charge into a hole. Accordingly, in recent years a pumping charge thereof has been carried out by use of their slurry characteristics.

Further, this slurry explosive is higher in explosion velocity and explosion power than ammonium nitratefuel oil explosives. Therefore, by employing such a slurry explosive composition, rocks may be finely crushed, and so the cost of boulder blasting can be greatly cut down. Additionally, the slurry explosive composition is higher in specific gravity than ammonium nitrate-fuel oil explo sives, and so is economical in transportation and boring costs.

The slurry explosives employed at the present time include types such as ammonium nitrate-TNT-water, ammonium nitrate-'I'NT-aluminum-water, ammonium nitrate-smokeless powder-water, ammonium nitrate-smokeless powder-alumnum-water, ammonium nitrate-aluminum-water, ammonium-nitrate-fuel oil-water, etc. However, from the view point of explosive powder and cost, etc, the ammonium nitrate-TNT (and/or aluminum)- water type is most effective and is most widely used.

These slurry explosives are known to be greatly influenced in explosive performance by their chemical compositions and their physical properties. For example, in

3,524,777 Patented Aug. 18, 1970 ice.

Annular Report No. 38 of the 1967 assembly of the Industrial Powder Association (Japan), it is taught that water and air interpose between the powder particles because the movement of the slurry explosive in a hole, particularly the replacement thereof for water and air, is not good at the time of filling the hole up. If the amount of Water or air interposed is over a certain limit, detonation is difficult. Such a phenomenon is recognized to originate from the fact that the viscosity of thickening agent used as a dispersion medium for obtaining a uniform composition of slurry explosive is too high.

However, in case the viscosity is too low, it becomes impossible to maintain a stable suspension of the slurry explosive, and then not only does storage become impossible, but also at the time of filling of a hole, sand and mud of the hole wall are mixed into the slurry composition, or else in water springs the explosive composition is dissolved out into the water and does not completely explode, or the explosion velocity is extremely lowered. These can be proven, for example, for the fact that it was stated at the 21st annual assembly of the Japanese Chemical Society that one of the causes for the explosion velocity of TNT type slurry explosives being rapidly lowered at about 250 cm. from the initiator is mixing of sand and water with the slurry explosive. Therefore, in the case of preparing the slurry explosive, it is important to determine the composition with careful consideration so that the composition has an appropriate viscosity.

In general, as a thickening agent blended in a slurry explosive, guar gum, carboxymethyl cellulose and other high molecular weight dispersing agents are known and used. However, these thickening agents in the slurry explosive are greatly deteriorated in viscosity after the preparation of the slurry explosive, and the viscosity at the time of using the explosive is occasionally lowered to about of the initial viscosity, and, in most cases, certain components contained therein are precipitated. As a method of improving such a defect, the use of an acrylamide gel as a thickening agent is described in the specifications of US. Pat. Nos. 3,097,120 and 3,097,121. However, acrylamide gel is a high molecular weight substance which is too expensive for practical use. The specification of U .8. Pat. No. 3,361,604 teaches the use of a naturally wetted fine fibrous pulpy substance for increasing vis cosity and improving suspension due to the interlacing force of the fibers. However, it is not effective, for practical use, to maintain the stability of slurry explosives by using these kinds of thickening agents. This is due to the fact that they must be used in too high a concentration for stabilization to be able to neglect a carbon source on the oxygen balance of the slurry explosive.

The object of the present invention is to provide a thickening agent for slurry explosives having the effect of in creasing the viscosity and gelation sufficiently to keep the slurry explosive stable at a uniform composition over a long period of time.

SUMMARY OF THE INVENTION The slurry explosive of the present invention is composed of:

(1) a composition consisting essentially of (a) ammonium nitrate, or a mixture of ammonium nitrate and an alkali metal nitrate, or a mixture of ammonium nitrate and an alkaline earth metal nitrate, or a mixture of ammonium nitrate and an alkali metal nitrate and an alkaline earth metal nitrate;

(b) at least one member selected from the group consisting of 2,4,6 trinitrotoluene, aluminum, smokeless powder and fuels; and

(c) water;

3 (2) 0.1. to 2.0% gaur gum; (3) not more than 0.3% of a borate or borates, and/or not more than 20% hexamethylene tetramine; and (4) 0.02 to 2.0% of an antimony compound or compounds, all percent being by weight.

DETAILED DISCLOSURE OF THE INVENTION The slurry explosive obtained by blending as the main components ammonium nitrate or ammonium nitrate and an alkali metal and/or an alkaline earth metal nitrate, at least one member selected from TNT, aluminum, smokeless powder and fuel, and water, under sufficient stirring, cannot be maintained at its appropriate viscosity and suspension disperibility even by blending therein guar gum as a thickening agent with stirring.

However, upon adding and blending therein a small amount of at least one borate selected from sodium borate, potassium borate, calcium borate and magnesium borate, with stirring, the borate functions as a cross-linking agent for the gaur gum to give a slurry explosive having temporarily good physical properties. However, deterioration of viscosity with lapse of time is inevitable. For example, according to the present inventors experiment, the viscosity of the slurry explosive obtained by mixing and dissolving 37 parts of water, adding and mixing 18 parts of prilled ammonium nitrate, 20 parts of TNT, 5 parts of aluminum powder, and 0.1 part of sodium borate thereto under sufiicient stirring changes with the lapse of time as shown in Table 1.

In the present invention, the viscosity was determined using a rotating cylindrical viscometer.

Also, it has been found that the deterioration of viscosity with the lapse of time is eifectively controlled by further adding at least one antimony compound selected from antimony potassium tartarate, antimony trioxide, antimony trisulfide, etc. to the guar gum-borate type slurry, thereby an appropriate viscosity and good dispersion state of the slurry explosive being kept over a long period of time.

According to an experiment by the present inventors, the slurry explosive obtained by adding 38.5 parts of powdery ammonium nitrate and 0.1 part of antimony trioxide to a solution of 0.3 part of guar gum in 20 parts of water and, after dissolving, dispersing therein 16 parts of prilled ammonium nitrate, 20 parts of TNT and 5 parts of aluminum powder therein, and adding 0.1 part of sodium borate, did not significantly change viscosity after as long as 30 days. In contradistinction, a slurry explosive obtained in the same manner except without adding antimony trioxide, TNT began to precipitate in about days because of a viscosity depression. Hexamethylene tetramine and antimony compounds, respectively, do not have a cross-linking effect of a guar gum-water solution, but hexamethylene tetramine has this effect on guar gumammonium nitrate-water solution upon adding at least one antimony compound. Further addition of a small amount of sodium borate, potassium borate, calcium borate, magnesium borate, etc. is effective for the cross-linking function of hexamethylene tetramine.

The amount of the present thickening agent to be effectively added to the slurry explosive is, by weight, 0.1 to 2.0% of guar gum, 0.02 to 2.0% of the antimony compound, not more than 0.3% of the borate, preferably 0.025 to 0.3% of the borate, and not more than 20% of hexamethylene tetramine. Although the range of the viscosity of a slurry explosive is difiicult to define, since it is varied depending on the charging method, storage temperature and the diameter of charging hole, the efiective range of viscosity is generally considered to be 10 to 1,000 polses.

TABLE 2 Sodium borate, percent by weight 0 0. O5 0. 08 O. 1 0. 12 0. 15 0. 20

Guar gum,

percent by weight: Poise No'rE.-Hyphens in the Table 2 show a viscosity more than 1,000 polses, where measurement was discontinued.

In this case, when the amount of sodium borate is above 0.2%, the viscosity of the composition decreases, and at lower temperatures, the thickening agent is coagulated. However, from the fact that when heating at 30 C. such a thickening agent is normal in state, it is believed that the amount thereof corresponds to the temperature of the place where the explosive is used. For the case when the guar gum content is above 2.0%, any further effect of increasing viscosity corresponding to an increase of the content could not be obtained. Considering an economical effect, about 0.3% by weight was found to be most effective.

Table 3 shows the viscosity measured at 25 C. of the compositions prepared by adding (separately) 0.1 part of antimony potassium tartarate, antimony trioxide and antimony trisulfide to 34.9 parts of an aqueous solution containing 0.3 parts of guar gum, and, after sufiiciently stirring, mixing not more than 20 parts of hexamethylene tetramine to cross-link therewith, and finally adding powdery ammonium nitrate thereto to make parts of an ammonium nitrate aqueous solution.

TABLE 3 Hexa-methyleue tetramine, percent by weight 0 4 6 8 By weight:

Poise This table shows that large differences in the effect according to the kind of antimony compound used were not found. In view of the viscosity of the slurry explosive, hexamethylene tetramine is efiectively used in an amount of 4 to 20%, however, in view of the relationship thereof with the oxygen balance, it is difficult to define the content from the view point of the viscosity only.

In this case, use of sodium borate serves to control the viscosity. The result of such an experiment is as shown in Table 4.

Table 4 shows the viscosity measured at 25 C. of a composition prepared by mixing 59 parts of powdery ammonium nitrate containing 0.01 to 0.05 part of sodium borate in 41 parts of an aqueous solution containing 0.3 part of guar gum, 0.1 part of antimony potassium tartarate and 6 parts of hexamethylene tetramine, under vigorous stirring.

the following examples; however, the present invention '1 BLE 4 A is not limited to these examples. Sodium borate, percent by weight 0.01 0.02 0.03 0.04 0. 05 EXAMPLE 1 Poise Guar gum and an antimony compound in an amount (Gum gum= 3% by as shown in the following table, and 37 parts of powdery weight)+(anttmortly ammonlum mtrate were mixed, and then water was added ggfifig ifi thereto. After stirring sufiiciently, 18 parts of prilled am- (hexamethylene monium nitrate, 20 parts of TNT and 5 parts of aluminum E: fi f f f ff3 17 25 33 160 230 380 powder were blended therein, and, after dispersing homogeneously, sodium borate or/ and hexamethylene tetramine were added thereto. Water was added in an Th S tab e confirms that the 1 of C0I{tf011111g the amount so that the total amount of guar gum, antimony Viscosity can be accompllshed y addmg a sllght amount compound, sodium borate, hexamethylene tetramine and of sodium borate. Water was parts. The slurry explosive obtained, after Table 5 shows the change in viscosity, measured at being allowed to stand under natural conditions, was C. of a composition contammg 6%, by weight, of measured with respect to the change in viscosity with hexamethylene tetramine, upon changing the content of lapse of time, and the following results were obtained. antimony potassium tartarate in the composition shown (The viscosity was measured at 25 C. by using a rotating in Table 3. cylindrical viscometer.)

TABLE Guar Sodium gum, borate. Antimony Hexamethy- Lapse of time, hr. percent percent compound, lene tetramine, No. wt. wt. percent wt. percent wt. 0 96 216 400 720 Poise 0.3 0.1 Antimony potassium 0 520 450 430 410 410 tartarate, 0.3. 0.3 0.1 Antimony potassium 0 550 450 410 380 370 tartarate, 0.2. 0.3 0.1 Antimony potassium 0 550 570 430 380 370 tartarate, 0.1. 0.3 0.1 Antimony potassium O 550 420 400 370 340 tartarate, 0.05. 0.3 0.1 Antimony trioxide, 0.5 0 500 400 400 370 380 0.3 0.1 Antimony trioxide, 0.2 0 520 500 420 350 320 0.3 0.1 Antimony trioxide, 0.1 0 500 480 400 350 320 0.3 0.1 .Aiatglfinony trioxide, 0 530 500 350 320 300 0.3 0.1 Agiz unony trisulflde, 0 550 460 400 340 300 0.3 0 Antimony potassium 4 43 52 48 43 tartarate, 0.1. 0.3 0 Antimony trioxide, 0.1 4 43 51 46 44 42 0.3 0 Argtilmony trisulfide, 4 42 52 47 43 34 0.3 0.03 Antimony potassium 3 410 380 350 330 300 tartarate, 0.1. 0.3 0.04 Antimony potassium 3 500 450 420 370 350 tartarate, 0.1. 0.3 0.1 Antimony potassium 0 550 110 32 14 3.8

tartarate, 0.

i This example is for reference.

TABLE 5 EXAMPLE 2 Antimony potassium tartarate (percent 0 3 Slurry explosive compositions A and B, shown in the y welgbt) 0 table below, were subjected to an explosion velocity Poise 5O measurement by the Dautriche method (35 mm. diameter (Gum :0.3%,by weight)+(hexa steel pipe) immediately after preparation, and also after methylene tetramine, 0% by weight) 0.2 15 16 17 storage for 26 days at an average temperature of 28 C.

The viscosity changes at above 0.1% of the content of antimony potassium tartarate. Therefore, in the case of using hexamethylene tetramine as a cross-linking agent, the optimum content of the antimony compound is about 0.1%.

Thus, the slurry explosive obtained by blending guar gum, the borate or/ and hexamethylene tetramine and the antimony compound is good in viscosity and suspending dispersion, and is stable in its physical properties and explosion effect over a long period.

In particular, as described in the specification of Japanese patent publication No. 4,235 65, hexamethylene tetramine is a good fuel, and a mixture of hexamethylcne tetramine and ammonium nitrate is a sensitizing agent. Therefore, a non-sensitive crystal produced by the repetitive process of dissolving and recrystallization of contained ammonium nitrate by temperature changes during the storage of a slurry explosive can be sensitized by adding and mixing hexamethylene tetramine therewith. Further, antimony trioxide is well known as a sensitizing agent, naturally occurs as gray antimony and, therefore,

is easily available.

The present invention will be further illustrated with The results are shown in the following table. Herein, aluminum powder had an average particle size of 325 mesh (JIS sieve) and the surface thereof was oxidized in the air. A No. 6 electric cap was used as the initiator and 15 g. of tetryl was used as the booster.

1 Not exploded completely.

Filling density and explosion values of two measurements.

As shown in the above table, the slurry explosive using the thickening agent cross-linked by hexamethylene tetramine increased sensitivity. That is, the slurry explosive containing aluminum powder whose surface is oxidized in the air, and which has been heretofore impossible to exvelocity are the average 7 plode completely in a small diameter, such as 35 mm., was sensitized during 26 days storage at an average temperature of 28 C.., so that the explosive can be completely exploded.

EXAMPLE 3 Three kinds of TNT-containing slurry explosives, A, B and C, as shown in the table below, were subjected to measurement of their explosion velocity by the Dautriche method (35 mm. diameter steel pipe). The results were as follows:

A,wt. B,wt. C,wt. percent percent percent Ammonium nitrate 55. 49. 0 46. TNT 25'. 0 25. 0 25. O Guar gum 0. 5 0. 5 0. 3 Antimony potassium tartarate. 0 0. 1 0 Hcxamethylene tetramine. O 6. 0 6. 0 CMO (carboxyrnethylcellulose) 0.5 0 0 Water 19. 0 10. 4 20. 2 Antimony trisulilde 0 0 2. 0

Filling density, g./ce 1. 36 1.37 1. 35 Explosion velocity, m./sec 3,200 3, 780

1 Not exploded completely.

The filling density and the explosion velocity are average values of two measurements.

A No. 6 electric cap was used as the initiator, and 15 g. of tetryl was used as the booster.

The powdery TNT used in the present example was low in sensitivity, and explosive A was not completely exploded. However, explosive B (containing hexamethylene tetramine) was more sensitive, and explosive C (containing antimony trisulfide) exhibited an even higher explosion velocity.

EXAMPLE 4 2 kg. of the slurry explosive having a composition shown in the following Table A was poured into a plastic pipe which had an 8 cm. diameter and a 60 cm. length, and which was previously filled with water. After closing the top of the pipe, the pipe was turned upside-down 10 times to slightly mix the explosive. The explosive was then removed and further poured into another pipe which had the same diameter mentioned above and a 120 cm. length, and which had previously been filled with water and sand having a 24 mesh (JIS sieve) average particle size, which settled down on the slurry explosive to make a 20 cm. deep sand layer.

The slurry explosive in the pipe was, 20 hours later, taken out quarter by quarter, and each quarter was named A, B, C and D from the bottom to the top of the explosive, respectively. The D part of the explosive layer (upper part) contained a small amount of sand.

The explosion velocity thereof Was compared with that of an untreated slurry explosive by the Dautriche method. The result is shown in the following table (Table B).

TABLE A Component: Parts Powdery ammonium nitrate 66 Aluminum powder 7 Guar gum 0.3 Hexamethylene tetramine 6 Antimony potassium tartarate 0.1 Water 20.6

TABLE 13 Filling Explosion density velocity (g./cm. (KL/S80.)

Considering that the treatment involved is very severe and that the explosion velocity of A, B, C and D had not deteriorated (in comparison with that of the untreated explosive), the slurry explosive of the present invention is recognized to have a good water bearing property.

As will be appreciated by one skilled in the art, the ammonium nitrate or mixture thereof with alkali or alkaline earth metal nitrates are known in the art as slurry ex plosives. Accordingly, the ratio of the ammonium nitrate, etc. to the TNT, aluminum, smokeless powder or fuels is not critical. However, it is most preferred for various reasons that the ratio of ammonium nitrate to alkali metal nitrate and/or alkaline earth metal nitrate is from 1:below 0.5. This range is not to be interpreted as limiting.

Slurry explosives comprising ammonium nitrate or mixtures of ammonium nitrate and an alkali metal nitrate or mixtures of ammonium nitrate and an alkaline earth metal nitrate, or mixtures of ammonium nitrate with both of the above, are known to the art. The particular ratios of ammonium nitrate to these is not important and is known to the art. Generally, the ratio of ammonium nitrate to these materials is within the range lzbelow 0.5.

Further, the ratio of ammonium, or the described mixtures, to the TNT, aluminum, smokeless powder or fuel is also not critical. Generally, however, the ratio of these components is from minus 25 to 15, preferably from minus 10 to 10, oxygen balance (ammonium nitrate or mixture, etc; TNT, etc.).

What we claim is:

1. A slurry explosive comprising (1) a composition consisting essentially of:

(a) a member selected from the group consisting of ammonium nitrate, a mixture of ammonium nitrate and an alkali metal nitrate, a mixture of ammonium nitrate and an alkaline earth metal nitrate, and a mixture of ammonium nitrate and an alkali metal nitrate and an alkaline earth metal nitrate,

(b) at least one member selected from the group consisting of 2,4,6-trinitrotoluene, aluminum, smokeless powder and fuel oils, and

(c) water,

(2) 0.1 to 2.0% of quar gum,

(3) at least one member selected from the group consisting of greater than 0% but not more than 0.3% of a borate or borates, and greater than 0% but not more than 20% of hexamethylene tetramine, and

(4) 0.02 to 2.0% of an antimony compound or compounds, all percents being by Weight.

2. A slurry explosive according to claim 1, wherein the borate is selected from the group consisting of sodium borate, potassium borate, calcium borate and magnesium borate.

3. A slurry explosive according to claim 1, wherein the antimony compound is selected from the group consisting of antimony potassium tartarate, antimony trioxide and antimony trisulfide.

4. The explosive of claim 1 wherein said borate is present in an amount of from about 0.025 to about 0.3% by weight.

5. The explosive of claim 1 wherein said hexamethylene tetramine is present in an amount of from about 4% to about 20% by weight.

6. The explosive of claim 1 wherein the viscosity thereof is from about 10 to about 1,000 poises.

References Cited UNITED STATES PATENTS 3,235,425 2/1966 Clemens et al. l4948 3,321,344 5/1967 Arbie 149-48 X 3,361,604 1/1968 Griflith l4944 CARL D. QUARFORTH, Primary Examiner S. J. LECHERT, JR., Assistant Examiner US. Cl. X.R.