US2470733A - Stabilized blasting explosive composition - Google Patents

Description

Patented May 17 1949 UNITED STATES TENT OFFICE STABILIZED BLASTING EXPLOSIVE COOSITION tion of Great Britain No Drawing. Application January 29, 1946, Serial No. 644,195. In Great Britain March 14, 1945 4 Claims.

The present invention relates to the production of improved blasting explosive compositions of the kind liable on prolonged heating to evolve oxides of nitrogen, and is especially applicable to blasting explosive compositions as aforesaid comprising nitric esters, ammonium nitrate, or metallic nitrates amongst their ingredients, and thus to most of the blasting explosives of commerce. Th invention relates more particularly to the stabilization of blasting explosive compositions as aforesaid for storage purposes.

Although various other factors can affect the stability of nitric esters and inorganic nitrates, it is Well known that traces of acids adversely affect the stability of explosives containing these ingredients, as evidenced by the increased, yield of oxides of nitrogen they eVOlVe when they are heated. Since it is impossible entirely to avoid the presence, or at least to prevent the development, of impurities of acid character in such explosive compositions, small amounts of faintly alkaline substances are frequently included as stabilizers, in explosive compositions of the kind described, for instance chalk or ammonium carbonate. On continued storage, however, much faintly alkaline substances become used up, and they do not prevent the development of acidity and the consequent evolution of oxides of nitrogen from continuing thereafter. The presence of an excessive alkalinity in the explosive composition may also accelerate its decomposition.

It has been proposed in British Patent No. 383,630 to include a small amount of one or more mildly alkaline phosphates in explosive compositions especially in those containing sodium nitrate contaminated with soluble magnesium and/or calcium salts; more particularly disodium hydrogen ortho-phosphate, diammonium hydrogen ortho-phosphate, or sodium ammonium hydrogen ortho-phosphate, and various explosives containing diammonium hydrogen ortho-phosphate have found successful application in practice. The bufiering action of these mildly alkaline phosphates satisfactorily prevent the development of acidity and they have a marked stabilizing action. Diammonium hydrogen orthophosphate, however, may evolve ammonia when it is heated; and under moist conditions the other mildly alkaline ortho-phosphates may react on heating with ammonium nitrate with the evolution of ammonia. More generally their initial alkalinity is higher than the most desirable level.

We have found that neutral mixtures of alkali metal dihydrogen ortho-phosphates with di-alkali metal hydrogen ortho-phosphates exhibit a desirable stabilizing action when present in ad- 2 mixture with the other ingredients of blasting explosive compositions of the kind described, with the added advantage that their buffering action maintains the explosive composition substantially neutral.

Thus, irrespective of the precise amount of the traces of acid or alkaline impurities that may be present in the other ingredients of the blasting explosive composition, the introduction results in a practically neutral explosive composition. One advantage of this is that even if the composition contains an ammonium salt such as ammonium nitrate, it will not readily evolve ammonia on heating. Moreover the use of faintly alkaline stabilizers of very low solubility, such as calcium carbonate, or the presence of traces of other alkaline substances will not render the composition appreciably alkaline When the neutral mixture of alkali metal dihydrogen orthophosphate and di-alkali metal hydrogen orthophosphate used according to the invention is incorporated in the composition. on the other hand, the explosive composition does not develop any appreciable acidity on storage and its stability characteristics are markedly improved.

The invention therefore comprises the inclusion in blasting explosive compositions of th kind liable on prolonged heating to evolve oxides of nitrogen, of small amounts of an alkali metal dihydrogen ortho-phosphate and a di-alkali metal hydrogen ortho-phosphate in relative proportions such as to give a neutral mixture of these salts.

In putting the invention into elfect it is preferred to employ a previously prepared neutral mixture of the alkali metal dihydrogen orthophosphate and di-alkali metal hydrogen orthophosphate. This mixture may conveniently be distributed through on or more of the non-explosive ingredients, if such are present, before bringing these into admixture with the explosive ingredients of the composition, in order to facilitate its distribution throughout the final composition. The alkali metal dihydrogen orthophosphate and the di-alkali metal hydrogen ortho-phosphate may if desired be employed each in its customary hydrated crystal form, or in the anhydrous form. An equimolecular mixture of sodium dihydrogen ortho-phosphate, monohydrate and disodium hydrogen orthophosphate dodeca-hydrate may be employed, advantageously using about 0.25 to 2.5 per cent of these hydrated salts, reckoned on the total weight of the explosive composition. The potassium salts, which are encountered in the anhydrous form, may also be used in equimolecular proportions in the equivalent percentages.

. ingredients-Z Theresulting explosives may be tested for sta-= 1 bility by exposing them in a vacuum at raised tempera'tures, forirrstance-GO. .C.. to 100 C., and

measuring. the. amount of gasevolved over suitable periods of time. The invention is illustrated in. the following examples in which the percentages are percentages by Weight.

Example 1 A gelatine explosive is made from the follow- Nitrated 80:20 mixture of glycerine and ethylene glycolh u 50 deoa. hydrate the-nitrocellulose is :dissolved; The viscou-s jelly I orxsolution-thereby formed is then transferred to .;a.McRQberts mixer-where the woodmeal. and

a. previously; preparednnixture of theammioziium nitrate and, the mixed ortho-phosphates. are

- :mixed into it. When-heated. ina; vacuum stabilitytest at." we =C..1I gramof the resulting gelatineexplosivegives a gas evolution 0163.4 cos. 'in- 8 hours, 9.7-ccs. in 16. hours and 21.4 'cc's. in

0.5 1 The. incorporation of :the ingredients, is carried out by first mixing thenitratedmixture oi gly .cerine and ethylene glycol with the so1uble-nitro cellulose; and allowing. the mixture tostand until 4 A jelly or.viscoussolution is first prepared from the nitrated mixture of glycerineand ethylene glycol, the liquid ,dinitrotoluenes and the nitrocellulose, andthe remaining ingredientsare then introduced into.= the jellyvor viscous solution in I I a McRoberts mixer Without the 'premixing of these ingredients other than the admixture of the two phosphates with one another. The resulting gelatine explosive is of neutral character and satisfactory explosive properties, It is also of excellent Sammy.- c

" Per cent- 24.:hours. ltsexplosiveproperties aresatisfactom; Itreactsneutrah a similar explosive composition in, which there is used an extra 0.5- percent ammonium Example 2 A. gelatine explosive is made from the fo11owma ingredients Per cent Nitrated 80:20 mixture of glycerine and ethylene glycol 34.0 Soluble nitrocellulose 1.0 Liquid mixture of dinitrotoluenes 1.8 Ammonium nitrate 35.8 Sodium nitrate 19.0 Woodmea1 7.6 Chalk 0.3

Equimolecular mixture of sodium dihydrogen ortho-phosphate monohydrate and disodium hydrogen ortho-phosphate' dodeca hydrate. 0.5

In th .v vacuum' stability' test carried out at Cnthe volume of gas evolved was 4.2 ccs.

in 8 hours; 12.4. ccs. in 16 hours. and 21. rice. in 24; hours, Whereas from a similar explosive compositionmade without the mixed phosphates g l but with an extra.0.5 per cent'ammonium hi trate-the corresponding gas volumes were respec- :tively; 8,6, cos, 16.2 ccs andmore than 25 cos,

We claim:

7 1. A blasting explosivexcomposition. comprising a. liquid explosive nitric ester, atleast one salt selected from. the group consist/ingot ammonium nitrate andiamixture of ammonium nitrate and sodiumnitrate. an.d'from10.25'to,2.5% by; weight I of} a substantially equimoleoularmixture of, at g least one clialkalihydrogenortho phosphateand; I

at least. one alkali. metal; dihydrogen ortho-phos-.

hhate.

2. A blasting plosive. Composition-comprise ing a liquid explosive; nitric ester, ammonium nitratefa'nd from 0:25 to,;2.5%; lay-weight of a substantially ,equimole-cular mixture of at. least: one dialkalii hydrogen. ortho-phosphate and at least one alkali metalqdihydrogen onthmphos-g phata,

31A blasting; explosive compositionas claimed in claim 2,. wherein disod'ium hydrogen olthos phosphatejdodeca hydrateand, sodiumdihsidro- 1 gen ortho pho'sphate mono-hydrate. are present in substantially equlmolecular proportions to form the mixture.

4. A blasting explosive composition comprisingnitroglycerine, ammonium. nitrate... and; from 0125 to 2.5% of a mixture ofisubstantially equimolecular quantities of sodium dihydrogenorthophosphate mono-hydrate andzdisodium hydrogen ortho-phosph-ate dodeca hydrate.

EDWARD" WI-IITWORTI-L; JiAMESIC. I-IORNEL.

REFERENGES GI'IED" The following references are of. record in: the file of..this patent:

UNITED. STATES PATENTS Number Name. Date 610,615, Stevens. Sept.,1 3,.1.898 8751913 Holmes in. Jan. '7, 1908 .2399 Morton. et. ah.-. e. June;.6, 1.9.33 1',927,832 Holines- Sept, 26,. i933 2008.808 Williams. Mimi. Ju1y.23, 19,35 2;.118566. Miles... May..24, 19.38 149304 Massucci.prions... Mar... 7; L 39 Q'IHER: .EREEERENCES:

Britten: Hydrogen Ion-s." .vol'.I,l3rd.ed. (1943), pages 300* and 308'... Copy in Division. 43'.