US3296042A

US3296042A - Explosive containing oxidizing salt, organic nitro-compound, and hydrophilic colloid

Info

Publication number: US3296042A
Application number: US355907A
Authority: US
Inventors: Quadflieg Therese; Wetterholm Gustav Allan
Original assignee: Nitroglycerin AB
Current assignee: Nitroglycerin AB
Priority date: 1964-03-30
Filing date: 1964-03-30
Publication date: 1967-01-03
Anticipated expiration: 1984-01-03

Description

(vide the, British Patent No. 597,716).

3,296,042 Patented Jan. 3, 1967 3 EXPLOSIVE CONTAINING OXIDIZING SALT, R-

GANICiNITRO-COMPOUND, AND HYDROPHIL- IC COLLOID ThereseQuadflieg, Frankfurham Main, Germany, and

\ Gustav Allan Wetterholm, Gyttorp, Sweden, assignors to. Nitroglycerin Aktiebolaget, a company of Sweden No Drawing. Filed Mar. 30,1964, Ser. No. 355,907

r 10 Claims. (Cl. 149-7) 1 This application is a continuation-in-part of our applicationfierial No. 561,982 filed January 30, 1956, now abandoned;

THE INVENTION BROADLY The present invention pertains to a plastic explosive comprising a mixtureof a solid explosive of high brisance having, in :a highly compressed condition, a detonation velocity exceeding 7,500 m./ sec. and at least one oxygendelivering, inorganic: salt incorporated in a gel produced from water and a hydrophilic colloid.

BACKGROUND OF THE INVENTION Plasticexplosives of this type are previously known They are produced .by first preparing a gel from water as the liquid constituent while employing a hydrophilic colloid as the gel-forming substance. Into the inexplosive gel thus 1 formed a high-explosive compound and one or more oxygen-delivering inorganic salts, such as nitrates and chlorates, are then kneaded. If desired, also other additional substances are added in suitable quantities.

Ini the patent referred to, there are set forth examples of explosives having the following composition:

Example 5 Example 6 Example 7 Example 8 Gel former 5 5 3. 7 3. 9

Oxidizing salt 15. 5 24. 0 11. 4 20.0

Water 2. 8 6. 1 2. 4 3.1

Explosive of high brisance 64 65. 0 73. 5 73 All these explosives; are strongly underbalanced with *respecttooxygen. Another characterizing feature is that they have a high content of explosive of high brisance. When. testing them, it has been found that, especially initwo respects, they do not possess sufficiently satisfactory properties to render them utilizable under practical conditions. 1111 order to be a safety explosive, an explosive should fulfill two essential requirements, namely, it shall have a lowsensitivity to mechanical influences, especially impact, but, it must be easy to initiate. It is in these two wrespects that the known explosives have proved unsatisfactory.

The: following two examples will confirm this fact.

Example 1 1 An explosive according to Example 7 of the British Patent No. 597,716, was made up:

. Percent Hexogem 73.5 Ammoniumnitrate 11.4 Ui'ea 5.7 Sodium acetate 3 aq 3.4 \Sddiumthiosulfate 5 aq 2.3

Starch 3.7

The water content of the explosive was 1.66 percent. On firing this explosive containing increasing contents of water with detonator No. 4, the following test results were obtained:

' Contentspf water Number of tests Number of detonations 1n the explosive, percent The above explosive, having a water content of 1.7%, was tested with respect of safety when being drilled on. These tests were carried out in such a way that drilling on an amount of 15-20 g. of the explosive inserted in a predrilled hole with a not preheated drill without crown was carried out for 60 seconds. Ten such tests were carried out with this explosive.

Results Amount Test time, sec.

Number of tests Number of denotations Example 2 An explosive according to Example 6 of the British Patent No. 597,716 was made up:

Percent Pentaerythritoltetranitrate 65.0 Ammonium nitrate 9.9 Calcium dinitrate 4 aq 20.1 Starch 5.0

On drilling-on testing this explosive, the following results were obtained:

Results Amount Test time, sec.

Number of tests Number of detonations THE OBJECT OF THE INVENTION The object of the present invention is to provide a plastic explosive composition of the above type having improved properties regarding the two factors above referred to, rendering them possible to use as explosives with improved safety.

THE INVENTION It has now been found that if the composition of the above explosives is changed insofar that the content of explosive of high brisance is lowered to values in the range of from 20 to 45 percent and, in combination therewith, the explosives are oxygen-balanced, the resulting explosive will be much more insensitive to mechanical influences, such as impact and drilling on, at the same time as it will maintain its property of being readily initiated. A condition that this result should be obtained is that the explosive of high brisance should not 'be a liquid nitrate ester. The explosive should thus be at least mainly free from nitroglycol and nitroglycerine. While in the known explosives the presence of such esters is not a disadvantage, the improvement according to the invention at least partially depends on absence of such esters.

It has especially been found that a safety explosive of the above type can be attained by an oxygen-balanced composition, in which the content of solid explosive of high brisance is from about 20 to about 45 percent by weight and the content of inorganic salt from about to about 70 percent by weight. The composition and amount of gel should be such that the water content of the explosive composition is within the range of 3-25% by weight. Furthermore, as mentioned, the explosive composition should be oxygen-balanced, whereby the composition will be insensitive to mechanical initiation even when being drilled on in a bore-hole. Despite its high content of water, the explosive composition and particularly despite its lower content of solid explosive of high brisance, the novel explosive compositions can be initiated with weak detonators.

THE OXYGEN-DELIVERING SALT Suitable inorganic oxygen-delivering salts are, especially such salts of alkali metals and alkaline-earth metals, for example, ammonium nitrate, calcium nitrate, sodium nitrate, barium nitrate or other nitrates, also calcium chlorate, potassium perchlorate, ammonium perchlorate or other chlorates and perchlorates. These substances are added in such quantities that the explosive is oxygenbalanced, for example in quantities between the limits 10-70%, preferably 30-65% by weight.

THE EXPLOSIVE OF HIGH BRISANCE As examples of explosives with high brisance used as components in the safety explosive according to the invention among other pentyl, hexogen, nitromannite, ditrinitroethylurea may be mentioned. Generally, such explosives with high brisance are particularly suitable which, when themselves in a highly compressed condition-corresponding to a density substantially within the range 1.45-1.65have a detonation velocity exceeding 7500 m./sec. The said explosive should be finely divided, but the degree of division is not critical.

THE HYDROPHILIC COLLOID Examples of suitable hydrophile colloids for producing the gel are starch and dextrin of different types, carboxymethyl cellulose, agar-agar, alginates, pectin, alkylcellulose, alkylhydroxylalkyl(ethyl)cellulose and other substances. One hydrophile colloid which has proved especially effective is guar gum. The guar may have been cross-linked by treatment with a cross-linking agent such as borate or chromate ions under alkaline conditions. The main ingredient of this material is galactomannan the content of which may amount to 78-82 percent, the balance being proteins fibers and moist. The quantity of the colloid in the explosive may vary between the limits 0.3 and 10% by weight.

OTHER POSSIBLE INGREDIENTS OF THE EXPLOSIVE COMPOSITIONS Further, the explosive may contain small quantities of additional substances usually included in explosives, for example organic flour, such as wood flour or rye flour and the like.

In certain cases it may also be desirable to add further substances which, without affecting the basic inventive principle, impart certain specially desirable characteristics to the explosive, for example, with respect to its resistance to cold, stability, etc. For this purpose additions to the gel of eutectic salt mixtures may be employed, and it has also been found advantageous for increasing the resistance to cold to add low molecular poly-hydric alcohols such as glycol or glycerin. To incerase the safety during the mixing of the components, the explosive with high brisance may be added in a partially phlegmatised form. As phlegmatising agents paraffin wax and waxes may be mentioned, for example. Moreover, a part of the final water content of the explosive may be added in such a way that the explosives with high brisance are added moistened with water.

The amounts of wax, paraffin wax and the like serving as phlegmatising agents and/ or coating agents may suitably be within the range 0.5-3% by weight.

-It is, of course, also possible to divide the salts during the manufacture of the explosives in such a way that a part is added to the gel in the form of a eutectic mixture and another part in solid form together with the highexplosive, in which case the latter part may be coated with water-repelling agents, as indicated above, and may also consist of ground salts.

PRACTICAL USE OF THE EXPLOSIVES The explosives according to the invention have proved to be useful for all kinds of normal rock blasting, for bulldozing and as explosives for gaseous coal mines. Naturally, the composition of the explosive is to be adapted to the field of utilization of the same.

PROPERTIES OF THE NOVEL PLASTIC EXPLOSIVE COM-POSITIONS The most remarkable property of the novel plastic explosive compositions is that they, despite a relatively low content of explosive of high brisance and a relatively high content of water, still possess a high power of initiation while being extraordinarily insensitive to mechancal stresses, patricularly when being drilled on in a bore-hole. In this connection, it has been found that explosive compositions disclosed in the above-mentioned British Patent No. 597,716 are, of course, sensitive to weak detonators, when they contain small amounts of water. If the content of water of these explosives is increased to values covered by the invention, the resulting explosive compositions will obtain a successively decreasing power of initiation. As will be evident from the test results in Example 3, the explosives according to the invention maintain their property of being initiated by weak detonators.

Example 3 An explosive of the following composition was made up:

This explosive was admixed with different amounts of water so as. to obtain representative values for a water content of the explosive between 3 and 25 percent. On

firing these mixtures with a detonator N0. 4 the following results were obtained:

Contents of water Number of in the explosive, Number of tests detonations percent The same resuults were obtained when rather than ditrinitroeth ylurea other explosives of high brisance were used; .in the explosive compositions according to the invention.

From a comparison between the explosive according to Example 1 above and the present explosive it is evident thatgthe latter are more readily initiated for higher contents of water within the field covered by the invention.

This explosive was subjected to the drilling-on test set forthin :Example 1. The following results were obtained:

Results Amount Test time, sec.

Number of tests Number of detonations Example An explosive of the following composition was made up:-

This explosive was subjected to the drilling-on test set' forth in Example 1. The following results were obtained:

Results Amount Test time, sec.

Number of tests Number of detonations Example 6 An explosive of the following composition was made up:

Percent Pentaerythritol tetranitrate 35.0 Parafiin 0.9 Ammonium nitrate 43.5 Calcium dinitrate 10.7 Glycerine 4.3 Starch 1.0 Water 4.7

This explosive was subjected to the drilling-on test setforth in Example 1. The following results were obtained:

Results Amount, g. Test time, sec.

Number of tests Number of detonations Example 7 An explosive of the following composition was made up:

This explosive was subjected to the drilling-on test set forth in Example 1. The following results were obtained:

Results Amount, g. Test time, sec.

Number of tests Number of detonations A series of further examples for manufacture of the explosives according to the invention are given below in tabular form. All samples were produced in a Mac- Roberts mixer in quantities of about 7 kgs. For this purpose the gel was first introduced, whereupon stirring was started and the remaining components were kneaded into the gel.

The explosive characteristics were determined by the following tests:

The detonation velocity was measured in a camera with a rotating mirror. The small lead block test was carried out according to Hess but with only 20 g. of explosive. The mortar values were obtained with a ballistic pendulum ofstandard construction and were related to the trotyl value (TNT). The gap tests were determined with cartridges, 25 mm. in diameter, at 20 C. The stability values were determined by measuring the loss of weight at C. for a loss of weight of 1% in a fiask of Pyrex glass having a diameter of 20 mm. and with a ground-in capillary of 0.2 mm. diameter and a length of 40 mm. Explosives made with different kinds of starch yield very similar results.

Composition, percent by Weight Ex. Oxygen delivering salts No. Components besides water Highly Parafiin brisant Colloid Polyhydric Organic wax, wax, H2O explosive NH4NO3 Ca(Na)2 alcohol flour etc.

or or NaNOs Ba(NOa)2 Pentyl, NH4NO3, Starch 42. 6 2. 8 12.0 Same as 8 32.0 5. 8 7. 8 Same as 8 21.0 8.2 7.3 Pentyl, NI'I4NO3, Pectin 42.4 3. 3 11.7 Dinitrinitroethylurea (DiTeU), 36. 0 3. 8 25.0

NH; N 0 Ethylhydroxyethylcellulose. 13 DiTeU, NH4NO treated with Wax, 31. 1 51. 9 3. 6 1.2 1.1 11.2

(zlvarboxymethylcellulosa Wood flour,

ax. 14 DiTeU, NH NO3, treated with par- 42.5 41.6 2.8 0.9 12.2

affin wax, Ethylhydroxyethylcellnlose, Paraflin wax. 15 Hexogen, phlegmatised with 2.5% 40. 6 41. 7 1. 3 3. 2 1.0 12. 1

paraffin wax, N aN O3, Starch, Rye flour, Wax. 16 Nitromannite, moist Starch, NH4NOa, 33. 3 32. 5 14. 3 1. 3 8. 7 0. 5 9. 5

Ca(NO3)2 in eutectic salt mixture, Rye flour, Paraflin wax. 17 DiTeU, phlegmatised with 2.5% 36. 3 17. 5 24. 7 9. 7 0.9 10. 8

paraffin wax, NH NO3, C3.(NO3)z, Starch, Wax. 18 DiTeU, phleg'matised with 2.5% 36. 5 40. 5 11.1 1. 0 4. 2 1. 7 5.0

parafin wax, NH4NO3, Ca(NOa)z, Agar-agar, Wood flour, Paralfin wax. 19 DiTeU, phlegmatised with 2.5% 41. 6 36. 1 10. 6 0. 9 5. 1 1. l 4. 6

paraffin wax, NH4NO3, C9.(NO3)2, Guar, Glycol, Wax. 20 DiTeU, moistened to 10%, phlegma- 33. 5 47.0 7.0 0.8 3. 7 1.7 6.4

tised with 2.5% paraffin wax, NH4NO3, Ca(NOa)2, Glycol, Wax. 21 Peptyl, phlegmatised, N H4NO3, 35. 0 43. 5 10. 7 1. 0 4. 3 0.9 4. 7

Starch, Glycerin, Paraflin Wax. 22 DiTeU, phlegmatised With 2.5% 39.0 38. 5 3. 0 5. 5 1. 0 13. 0

paraflin wax, K0103, Starch, Glycol. 23 DilcU, phlegrnatised with 2.5% par- 39.0 33. 5 3.0 1. 5 1.0 22.0

aflin wax, Ba(NOs)2, Starch, Glycol, Parafin wax.

Impact Tests of explosive characteristics sensitivity Stability test, per- Excess of Cartridge, at 80 0., Ex. cent det- Consistency oxygen, Volume Detonation velocity Small lead Mortar Gap test 1% short N o. onation percent weight, (camera) block test test, per- (25 mm. weight per cm. g. /cm. according cent of cartridge) after length of to Hess (20 TNT mm. honrs fall Density M./s. g.), mm.

8 0/60 Plastic 0. 9 1. 47 1. 42 6, 100 29. 0 126 70-90 360 1. 51 6, 600 12 0/60 Plastic to semiplastic 1.1 5,200 16.5 93 0 13 0/60 Plastic 1. 2 1. 43 2 6, 200 16. 5 116 20-30 10 Example 24 Composition, percent by weight Oxygen delivering salts Components besides water Highly brisant Colloid Polyhydric explosive NHrHNa or Ca(N0a)z 0r alcoh NaNO Ba(N0s)2 or chlorate DiIeU, phlegmatised with 2.5% garafi'ln wax, NH4 104, NaNOa, Starch, Glycol 39.4 17. 0 23.6 2. 0 7, 1

What we claim is:

1. HA novel plastic explosive having low sensitivity when being drilled-on in combination with ease and reliability of detonation by weak blasting caps mainly consisting of (a). from about 20 to about 45% by weight of a finely divided solid explosive ingredient of high brisance selected from the group consisting of pentyl, hexogen, nitrornannite, ditrinitroethylurea and having ,at a density above 1.45 g./cc. and detonation velocity exceeding: about 7500 m./second;

(b): at least one oxygen-delivering inorganic salt selected from the group consisting of nitrates, chlorates; and perchlorates of alkali metals and alkaline earth metals in an amount of from about to about 70% by weight, and

(c). a gel produced from water and a hydrophilic colloid selected fromthe group consisting of starch, dextrin, 1 carboxymethyl-cellulose, agar-agar, alginates, pectin, ,alkyl cellulose, alkyl-hydroxyalkyl (ethyl) cellulose, guar gum and cross-linked guar gum, the composition and the amount of said gel being such that the water content of the explosive is within the range of from about 3 to about 25% by weight and the hydrophilic colloid ranges between about :0.3.and 10%by weight,

said composition being oxygen-balanced and substantially free from liquid esters of nitric acid.

2..1An explosive .composition according to claim 1 Whereinysaid finely-divided solid explosive ingredient of high brisance is ditrinitroethylurea.

3.An explosive composition according to claim 1 whereinusaid finely-divided solid explosive ingredient of high brisance is pentyl.

4.11An explosive .composition according to claim 1 Example 24-Continued Composition, percent by weight Impact sensitivity test, Excess of oxypercent deto- Consistency gen, percent Organic flour Paraffin wax, H O nation per cm.

wax, etc. length of fall None 1. 0 9. 9 Plastic 1. 0

Tests of explosive characteristics Stability at Cartridge, volume Detonation velocity Small lead 8 0., 1%

weight gJem. (camera) block test Mortar test, Gap test short weight according to percent of (25 mm. carafter hours Hess (20 g.) TNT tridge) mm. Denslty M./s. mm.

wherein the amount of oxygen-delivering inorganic salt is from about 30 to about by weight.

5. An explosive composition according to claim 1 wherein the colloid is starch.

6. An explosive composition according to claim 1 wherein the colloid is guar gum.

7. An explosive composition according to claim 1 wheren the explosive ingredient of high brisance is present in a partially phlegmatised condition.

8. An explosive composition according to claim 1 wherein the inorganic salt is at least partly ammonium nit-rate.

9. An explosive composition according to claim 1 wherein the salt is at least partly coated with a waterrepelling substance selected from the group consisting of wax, paraifin wax and silicones.

10. An explosive composition according to claim 1 which additionally contains an antifreezing agent selected from the class consisting of glycol and glycerine.

References Cited by the Examiner UNITED STATES PATENTS 2,048,050 7/1936 Baker 149-7 2,167,679 8/1939 Rinkenbach et al 149-92 2,548,693 4/ 1951 Whetstone et a1 149-47 2,817,581 12/1957 Rinkenbach et al. 14947 FOREIGN PATENTS 597,716 2/ 1948 Great Britain.

CARL D. QUARFORTH, Primary Examiner.

BENJAMIN R. PADGETT, Examiner.

S. I. LECHERT, JR., Assistant Examiner.

Claims

1. A NOVEL PLASTIC EXPLOSIVE HAVING LOW SENSITIVITY WHEN BEING DRILLED-ON IN COMBINATION WITH EASE AND RELIABLITY OF DETONATION BY WEAK BLASTING CAPS MAINLY CONSISTING OF (A) FROM ABOUT 20 TO ABOUT 45% BY WEIGHT OF A FINELY DIVIDED SOLID EXPLOSIVE INGREDIENT OF HIGH BRISANCE SELECTED FROM THE GROUP CONSISTING OF PENTYL, HEXOGEN, NITROMANNITE, DITRINITROETHYLUREA AND HAVING AT A DENSITY ABOUT 1.45 G./CC. AND DETONATION VELOCITY EXCEEDING ABOUT 7500 M./SECOND; (B) AT LEAST ONE OXYGEN-DELIVERING INORGANIC SALT SELECTED FROM THE GROUP CONSISTING OF NITRATES, CHLORATES, AND PERCHLORATES OF ALKALI METALS AND ALKALINE EARTH METALS IN AN AMOUNT OF FROM ABOUT 10 TO ABOUT 70% BY WEIGHT, AND (C) A GEL PRODUCED FROM WATER AND A HYDROPHILIC COLLOID SELECTED FROM THE GROU PCONSISTING OF STARCH, DEXTRIN, CARBOXYMETHYL-CELLULOSE, AGAR-AGAR, ALGINATES, PECTIN, ALKYL CELLULOSE, ALKYL-HYDROXYALKYL (ETHYL) CELLULOSE, GUAR GUM AND CROSS-LINKED GUAR GUM, THE COMPOSITION AND THE AMOUNT OF SAID GEL BEING SUCH THAT THE WATER CONTEND OF THE EXPLOSIVE IS WITHIN THE RANGE OF FROM ABOUT 3 TO ABOUT 25% BY WEIGHT AND THE HYDROPHILIC COLLOID RANGES BETWEEN ABOUT 0.3 AND 10% BY WEIGHT, SAID COMPOSITION BEING OXYGEN-BALANCED AND SUBSTANTIALLY FREE FROM LIQUID ESTERS OF NITRIC ACID.

9. AN EXPLOSIVE COMPOSITION ACCORDING TO CLAIM 1 WHEREINN THE SALT IS AT LEAST PARTLY COATED WITHA WATERREPELLING SUBSTANCE SELECTED FROM THE GROUP CONSISTING OF WAX, PARAFFIN WAX AND SILICONES.