04/843805

11/02/1971

07/22/1969

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Hercules Incorporated (Wilmington, DE)

149/41

149/61, 149/75, 149/44, 149/42, 149/46, 149/77, 149/76, 149/60

B01F17/00; C06B11/00

149/44,46,60,61,75,76,41,42,77

Sebastian, Leland A.

What I claim and desire to protect by Letters Patent is

1. A process for the manufacture of a gelled inorganic oxidizer salt explosive of the aqueous slurry type containing a hydrocarbon oil as a fuel and having improved stability to syneresis, comprising admixing said hydrocarbon oil as an oil-in-water-type emulsion maintained by at least one nonionic-acyclic-type emulsifying agent selected from the group consisting of polyoxyethylene esters, polyoxyethylene alcohols, and polyoxyethylene ethers having a hydrophilic-lipophilic balance of from 15 to 20, with a mass of the remaining ingredients of said slurry including a cross-linkable galactomannan gum as a gelation agent and a cross-linking agent therefor when said gelation agent is in a weight ratio to said cross-linking agent of from 30:1 to 70:1 and comprises from 1 to 3 weight percent of the finished explosive; and maintaining the total resulting explosive ingredient mixture under conditions for said cross-linking.

2. A process of claim 1 wherein said hydrocarbon oil is a fuel oil.

3. A process of claim 1 wherein said galactomannan is a guar gum.

4. A process of claim 3 wherein said cross-linking agent is potassium pyroantimonate, and said hydrocarbon oil is a fuel oil.

5. A process of claim 4 wherein cross-linking of said guar gum is carried out at a pH of from 2.5 to 4; and wherein the content of said guar gum is within the range of from 1:5 to 2.5 percent and said ratio of guar gum to potassium pyroantimonate is within the range of from 50:1 to 70:1.

6. A process of claim 5 wherein said nonionic emulsifier is selected from the group consisting of a polyoxyethylene lauryl ether, a polyoxyethylene stearate and a polyoxyethylene glyceride ester.

7. In a process of claim 6, forming said total resulting admixture comprising, on a weight basis, from 8 to 30 percent water, from 40 to 80 percent inorganic oxidizer salt, from 0 to 30 percent of a particulate metal energizer and/or sensitizer, from 1 to 6 percent fuel oil and from 1.5 to 2.5 percent guar gum in a ratio to said pyroantimonate of from 50:1 to 70:1.

8. A process of claim 7 wherein at least a major proportion of said inorganic oxidizer salt is ammonium nitrate.

9. A process of claim 7 wherein said inorganic oxidizer salt comprises ammonium nitrate and sodium nitrate.

10. A process of claim 9 wherein said ammonium nitrate is in a weight ratio to said sodium nitrate of from 2:1 to 6:1.

11. A gelled inorganic oxidizer salt explosive of the aqueous slurry type containing a hydrocarbon oil as a fuel and having improved stability syneresis prepared by admixing said hydrocarbon oil as an oil-in-water-type emulsion maintained by at least one nonionic-acyclic-type emulsifying agent selected from the group consisting of polyoxyethylene esters, polyoxyethylene alcohols, and polyoxyethylene ethers having a hydrophilic-lipophilic balance of from 15 to 20, with a mass of the remaining ingredients of said slurry including a cross-linkable galactomannan gum as a gelation agent and a cross-linking agent therefor when said gelation agent is in a weight ratio to said cross-linking agent of from 30:1 to 70:1 and comprises from 1 to 3 weight percent of the finished explosive; and maintaining the total resulting explosive ingredient mixture under conditions for said cross-linking.

12. A gelled inorganic oxidizer salt explosive of claim 11 prepared when said hydrocarbon oil is a fuel oil, said galactomannan is a guar gum, and said cross-linking agent is potassium pyroantimonate.

13. A gelled inorganic oxidizer salt of claim 11 prepared so as to contain, on a weight basis, from 40 to 80 percent total inorganic oxidizer salt, from 0 to 30 percent of a particulate metal energizer and/or sensitizer, from 1 to 6 percent of said fuel oil, and to have a cross-linking density provided by the presence of from 1.0 to 2.5 percent guar gum and a sufficient amount of potassium pyroantimonate to provide said guar gum to potassium pyroantimonate weight ratio within the range of from 50:1 to 70:1

14. A gelled inorganic oxidizer salt of claim 13 containing ammonium nitrate as at least a major proportion of said inorganic oxidizer salt.

15. A gelled inorganic oxidizer salt explosive of claim 13 containing ammonium nitrate and sodium nitrate as ingredients of said inorganic oxidizer salt component.

16. A gelled explosive of claim 15 containing said ammonium nitrate in a weight ratio to said sodium nitrate of from 2:1 to 6:1.

This invention relates to the manufacture of gelled inorganic oxidizer salt explosives of the aqueous slurry type containing a hydrocarbon oil as a fuel component, and to gelled explosives so produced. In another aspect this invention relates to a method for incorporating a hydrocarbon oil, as a fuel, into a gelled aqueous inorganic oxidizer salt explosive, providing product having stability to syneresis greater than that of such hydrocarbon oil-containing explosives heretofore. Other aspects will be apparent in light of the accompanying disclosure and the appended claims.

Gelled inorganic oxidizer salt blasting compositions of the aqueous slurry type have had extensive use in the explosives industry in recent years. These compositions comprise an inorganic oxidizer salt, water, fuel, an additional sensitizer when necessary, and a gelation agent, generally in cross linked form.

Hydrocarbon oils, often of the fuel oil grade, have been utilized as fuels in gelled-aqueous-slurry-type inorganic salt explosives. However the hydrocarbon oil, due to its water immiscibility has generally been incompatible with the gel to the extent that it separates from the main body of explosive with loss in uniformity of oil distribution throughout, and accompanying loss in sensitivity of, the explosive.

This invention is concerned with a method for the manufacture of hydrocarbon oil-containing aqueous-gelled-type explosives, above described, providing for a uniform and stable dispersion of the oil substantially without syneresis, and hence without loss in sensitivity up to and including the time of shooting; and, with explosive product so produced.

In accordance with the invention, a process is provided for the manufacture of gelled inorganic oxidizer salt explosives of the aqueous slurry type containing a hydrocarbon oil as a fuel and having improved stability to syneresis, comprising admixing said hydrocarbon oil as an oil-in-water-type emulsion maintained by at least one nonionic acyclic-type emulsifying agent also referred to herein as "emulsifier," or "surfactant," selected from the group consisting of polyoxyethylene esters, polyoxyethylene alcohols, and polyoxyethylene ethers, having a hydrophilic-lipophilic balance (HLB) of from 15 to 20, with a mass of the remaining ingredients of said slurry including a cross-linkable glactomannan gum as a gelation agent and a cross-linking agent therefor when said gelation agent is in a weight ratio to said cross-linking agent of from 30:1 to 70:1 and comprises from 1 to 3 weight percent of the finished explosive; and maintaining the total resulting explosive ingredient mixture under conditions for said cross-linking. Also provided in accordance with the invention are gelled inorganic oxidizer salt compositions stable to syneresis over prolonged periods, and produced in accordance with the method above described.

As is well known, emulsifiers, as surface-active agents, are divided according to their structure into ionic and nonionic classifications, and each contains a lipophilic group and a hydrophilic group, the balance of which determines the relative simultaneous attraction of the emulsifier for water and for oil in an oil-in-water emulsion system. The HLB number as utilized herein and as recognized in the art, is a measure of hydrophilic-lipophilic balance of the emulsifier and is expressed as a value on a scale of from 1 to 20, the higher the number on the scale, the greater the hydrophilic character. A further discussion of HLB is noted in the Kirk-Othmer-Encyclopedia of Chemical Technology, Vol. 8 pages 131 through 132 inclusive wherein the above aspects of HLB are completely described.

The invention is based on my discovery that when a hydrocarbon oil-containing gelled aqueous inorganic oxidizer salt explosive in which the gelation agent is a cross-linked gelactomannan gum, is prepared by first forming an emulsion of the hydrocarbon oil in at least a portion of the water component in the presence of an above-described emulsifying agent, and the resulting emulsion is then incorporated with the remaining ingredients into the final explosive product, and when the cross-linking density of the gum gelation system is maintained by the presence of 1 to 3 weight percent gum in a weight ratio to a cross-linking agent therefor of 30:1 to 70:1, the resulting gelled explosive product has an unexpectedly high stability to syneresis.

Now-preferred emulsifying agents utilized in practice of the invention are a polyoxyethylene lauryl ether having an HLB number of 16.9 and commercially available as Brij 35; a polyoxyethylene stearate having an HLB number of 17.9 and commercially available as Myrj 53; a poloxyethylene glyceride ester having an HLB number of 18.1 and commercially available as G-1300; and a polyoxyethylene stearate having an HLB number of 16.9 and commercially available as Myrj 52. Further exemplary of emulsifying agents utilized in practice of the invention are a polyoxyethylene stearyl ether having an HLB number of 15.3 and commercially available as Brij 78; a polyoxyethylene fatty alcohol having an HLB number of 15.4 and commercially available as Emulphor ON-870; a polyoxyethylene glycol monopalmitate having an HLB number of 15.5 and available as Atlas G-2079; a polyoxyethylene cetyl ether having an HLB number of 15.7 and commercially available as Brij 58; and a polyoxyethylene monostearate having an HLB number of 16.0 and commercially available as Myrj 51. The foregoing exemplary emulsifying agents are manufactured by Atlas Chemical Industries except for Emulphor ON-870 which is manufactured by General Aniline & Film Corporation.

Potassium pyroantimonate is a now-preferred cross-linking agent for use in practice of the invention. However any suitable cross-linking agent generally utilized for cross-linking a galactomannan gum, as a gelation agent in aqueous inorganic oxidizer salt explosive compositions, can be utilized; and in such instances, as is well known, it is often necessary to adjust pH of the gelation system for optimum cross-linking reaction. Exemplary of such suitable and well-known cross-linking agents, in addition to the now-preferred potassium pyroantimonate, are those which liberate bismuth and antimony ions such as antimony sulfate and bismuth nitrate, and those which liberate borate, chromate and dichromate ions such as borax, zinc chromate, barium chromate, and potassium dichromate.

Exemplary, and now-preferred, galactomannan gum components of the gelled explosive, in accordance with the invention, are guar and locust bean gums.

Any petroleum fraction, suitable as a fuel component in aqueous-gelled-slurry-type inorganic oxidizer salt explosives, can be used in practice of the invention, exemplary of which are paraffin oil, diesel oil, fuel oil, and the like. A fuel oil of No. 2 to No. 4 grade is often advantageously utilized. The amount of hydrocarbon oil utilized is generally that providing the necessary balance for the oxygen supplied by the inorganic salts, and based on the complete explosive, can be as low as 1 percent and as high as 14 to 15 percent dependent upon the proportion of any supplemental fuels utilized, as for example particulate aluminum, silicon, or the like.

Although ammonium nitrate, alone or with sodium nitrate, often in a weight ratio thereto of from about 2:1 to 6:1 is in most instances the inorganic oxidizer salt component, other inorganic oxidizer salts can be utilized alone or with ammonium nitrate as a supplementary oxidizer salt, the alkali metal nitrates being now preferred. Exemplary inorganic oxidizer salts that can be used along or together with ammonium nitrate are alkali metal and alkaline earth metal nitrates, and perchlorates (including ammonium) as, for example, sodium nitrate, magnesium nitrate, potassium nitrate, barium nitrate, ammonium perchlorate, calcium perchlorate and magnesium perchlorate.

Now-preferred compositions produced in practice of the invention are those, on a weight basis, including from 8 to 30 percent water, up to about 30 percent of a suitable particulate metal as an energizer and/or sensitizer, generally aluminum, silicon, aluminum alloys, silicon alloys and the like, from 40 to 80 percent of total inorganic oxidizer salt, from 1 to 6 percent of a fuel oil grade of hydrocarbon oil, as the hydrocarbon oil fuel component, and from 1.5 to 2.5 percent guar gum with potassium pyroantimonate as a cross-linking agent therefor.

It is to be understood that any one or more of suitable supplemental fuels, energizers and sensitizers, aeration agents, and the like, all well-known ingredients for gelled-aqueous-slurry-type inorganic oxidizer salt explosives can be utilized in the formulation of explosive product in practice of the invention. Thus exemplary of such supplemental materials are powdered coal, particulate metals such as aluminum, magnesium-aluminum alloys, silicon alloys, ethylene glycol, DNT oil and the like; and sodium bicarbonate, sodium nitrite, and the like as aeration agents. Aeration agents advantageously utilized for in situ gas generation include sodium bicarbonate as disclosed in the Ferguson et al. U.S. Pat. 3,288,658, sodium nitrite as disclosed in the Albert U.S. Pat. 3,390,031 and sodium nitrite-sodium bicarbonate mixtures as disclosed in the Albert et al. U.S. Pat. 3,390,032. The use of sulfamates and/or sulfamic acid for the acceleration of the aeration rate when employing sodium nitrite as an aeration agent is disclosed in the Knight U.S. Pat. 3,442,729.

The gelled compositions produced in accordance with the invention are generally insensitive to detonating action of a No. 8 commercial blasting cap, but are detonatable by conventional "booster" charges of PETN (pentaerythritol tetranitrate), RDX (cyclotrimethylene trinitramine), Pentolite (PETN-TNT, 50/50), tetryl, Composition B (RDX-TNT 60/40) and the like.

In preferred practice, the explosive compositions of the invention are of the well-known class of nitrocarbonitrates by which term is meant there are no sensitizers which in themselves are high explosives and the mixtures will not detonate with a No. 8 blasting cap when packed for shipment.

Any suitable procedure can be utilized in carrying out the method of the invention, provided that the hydrocarbon oil is introduced into the mixing zone as a component of the emulsion, as above described. However the cross-linking agent is generally the last-added ingredient in order to assure uniform distribution of all ingredients prior to any impairment thereof that might be caused by premature gel formation.

The following procedure is exemplary of a now-preferred embodiment for manufacture of the explosive compositions in accordance with the invention, utilizing guar gum as the cross-linkable galactomannan gum together with potassium pyroantimonate as the cross-linking agent therefor:

Premixing

1. Dissolve the surfactant in from about one-fourth to one-half the portion of contemplated amount of water ingredient and add the hydrocarbon oil to the resulting surfactant-water mixture with stirring, and then emulsifying the resulting surfactant-containing mixture by passing it through a conventional homogenizer.

2. Admix ammonium nitrate, as the major inorganic oxidizer salt ingredient with a small proportion of ammonium sulfamate, the latter as an accelerator for subsequently described aeration, and with all but a small remaining portion of the water ingredient. Add fumaric acid to the resulting ammonium nitrate-ammonium sulfamate-water mixture in an amount sufficient to adjust the pH of that mixture to about 2.5 to 4.

3. Disperse dry guar gum as a gelation agent in dry sodium nitrate as a supplemental inorganic oxidizer salt, and

4. Disperse potassium pyroantimonate as a cross-linking agent for the guar gum, and sodium nitrite as the aeration agent, in the remaining water ingredient proportion.

Mixing

Admix the dry sodium nitrate-guar gum mixture with the ammonium nitrate-water-ammonium sulfamate mixture with agitation at 80° - 90° F. Add the fuel-water emulsion to the resulting water mixture of guar gum, sodium nitrate, and ammonium nitrate with continuous agitation. Add the potassium pyroantimonate-sodium nitrite mixture to the total ingredient mixture already formed, as described, with continued agitation for 10 to 15 minutes.

The final slurry product mixture, due to initial hydration of the guar gum, is stable to settling of ingredients while standing, but is still readily pumpable during which time the slurry can be pumped to emplacement for completion of cross-linking to form the gelled composition containing the fuel oil uniformly dispersed in form of small droplets, of size not exceeding about 25 microns, and stable to syneresis over prolonged periods.

After about 1 hour the cross-linking reaction at the pH level, adjusted as above described, is complete and the gelled composition is ready for detonation.

The invention is further illustrated with reference to tables 1-4 following.

Three formulations, Nos. A-1, A-2 and A-3 (see table 1) were prepared in accordance with the above-described procedure, and detonated, the formulations differing only in respect of the degree of aeration of each, and hence specific gravity. In carrying out the procedure, the hydrocarbon oil emulsion was formed from 22.7 grams surfactant, 5 pounds of No. 2 fuel oil, and 6.0 pounds water. The ammonium nitrate-ammonium sulfamate-fumaric acid mixture was formed from 61 pounds ammonium nitrate, 150 grams ammonium sulfamate and 9 pounds water, with sufficient fumaric acid to adjust the pH of the mixture to 3.0. The guar gum-sodium nitrate mixture was formed from 16 pounds sodium nitrate and 1.0 pound natural guar gum. The sodium nitrate-potassium pyroantimonate was formed from 10.4 grams potassium pyroantimonate and 45.4 grams sodium nitrite in 1.0 pound water.

Also, three conventional formulations, Nos. C-1, C-2 and C-3 (see table 1), similar to formulations A-1, A-2 and A-3 except that they contained ethylene glycol in lieu of fuel oil and differed slightly in respect of density, were prepared and detonated as "controls" for further evaluation of the A-1, A-2 and A-3 formulations.

The above formulations are shown in table 1 together with a summary of associated test data. ##SPC1##

As shown in table 1, the fuel oil-containing slurry product compositions of the invention, as further illustrated with reference to conventional ethylene-glycol-containing slurries (no hydrocarbon oil component) exhibit comparable gel stability, and high resistance to syneresis.

Several 100 -gram batches of gelled explosive product of the invention were made up in accordance with procedure described with reference to table 1 utilizing the same ingredients and ingredient proportions, and under the same conditions, as shown for the formulations A-1, except that a different emulsifier was utilized in each batch in an amount of 0.25 percent based on the weight of the entire formulation. Each formulation was allowed to stand over a prolonged period; and during intervals of that period, the formulation was examined for syneresis. The results of the test are summarized in table 2. ##SPC2##

Four acyclic surfactants utilized in practice of the invention are illustrated in tests 1-4 incl. of table 2. In each of tests 1-4 the HLB of the surfactant was over 15, the proportion of guar gum gelation agent was 1.5 percent with the ratio of guar gum to potassium pyroantimonate of 65:1, and all tests showed excellent resistance to syneresis. In the utilization of the remaining emulsifying agents shown (tests 5-10), all of cyclic structure, failed to sustain low syneresis; and even the cyclic-type surfactant of test No. 5 with an HLB of 16.7 showed serious syneresis initially after formulation.

A series of explosive compositions was prepared in accordance with the procedure above described with reference to table 1 each of which was the same as formulation A-1 except that the content of guar gum was varied, together with variance in the weight ratio of guar gum to the cross-linking agent, potassium pyroantimonate. Each formulation was allowed to stand over a prolonged period during intervals of which it was observed for syneresis and gel condition. The tests are summarized in table 3. ##SPC3##

The data of table 3 illustrate guar gum as the gelation agent at contents of 1, 1.5 and 2.0 percent in combination with potassium pyroantimonate as cross-linking agent therefor at three different guar gum: cross-linking agent ratios. The data demonstrate correlation of guar gum content with the ratio of guar gum to cross-linking agent. Thus at a 1 -percent guar gum content and at a ratio of 17:1, syneresis was serious after 3 days' storage whereas after 5 to 7 days' storage at a higher ratio, i.e. 33:1 and 67:1, there was very little syneresis. Upon increase of the guar gum content to 1.5 percent at a ratio of 333:1, very little syneresis was observed after 7 days and at the ratio level of 67:1 very little syneresis was observed after 96 days. Upon increase of the guar gum content to 2.0 percent at the higher ratio levels very little syneresis was observed after periods of from 98 to 104 days. In general practice, although guar gum content can be correlated with weight ratio of guar gum to cross-linking agent therefor to utilize a content of guar gum from about 1.0 to 3.0 percent over a broad range of ratios of 30:1 to 70:1, a gum content in the order of 1.5 to 2.5 percent in combination with a guar gum to cross-linking agent weight ratio of from about 50 to 70 is particularly advantageously utilized.

The data of table 3 demonstrate the combination of specific range of cross-linking density with use of an above-described emulsifying agent, in practice of the invention, to provide gelled aqueous hydrocarbon oil-containing explosive product having high stability to syneresis.

It will be evident to those skilled in the art, various modifications can be made or followed, in light of the foregoing disclosure and discussion without departing from the spirit or scope of the disclosure or from the scope of the claims.