Classifications

• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B47/00—Compositions in which the components are separately stored until the moment of burning or explosion, e.g. "Sprengel"-type explosives; Suspensions of solid component in a normally non-explosive liquid phase, including a thickened aqueous phase
  • C06B47/14—Compositions in which the components are separately stored until the moment of burning or explosion, e.g. "Sprengel"-type explosives; Suspensions of solid component in a normally non-explosive liquid phase, including a thickened aqueous phase comprising a solid component and an aqueous phase

Definitions

• Salt type explosives of the aqueous slurry type include the oxidizer salt, water and sensitizer components, often with a thickener and one or more of supplemental fuel, salt and energizing ingredients, and have had extensive use in recent years.
• These aqueous slurry explosives are often cap sensitive, although generally they are not detonatable by direct action of a No. 8 commercial blasting cap, but they are detonatable in response to action of a suitable booster charge.
• the sensitizer is generally smokeless powder, a high explosive such as TNT or PETN, or a nonexplosive such as particulate aluminum, DNT oil and the like; and, in numerous instances, gas bubbles are present to enhance sensitivity.
• a separate fuel component is often utilized for suitable oxygen balance and to provide supplemental energy properties.
• the explosive contains a gelation agent as a thickener component, often in crosslinked form and in at least a sufficient amount to cause the slurried ingredients to be retained in aqueous suspension.
• the oxidizer salt component is of the inorganic oxidizer and/or oxidizer-fuel types, exemplary of which are alkali metal, ammonium, and alkaline earth metal nitrates, and alkylamine nitrates, respectively.
• Guar gum has been widely used as a gelation agent for the above described salt type explosives, generally crosslinked with a suitable crosslinking agent exemplary of which are those of US. Pat. No. 3,301,723.
• a suitable crosslinking agent exemplary of which are those of US. Pat. No. 3,301,723.
• chromium salts have been proposed as crosslinking agents for guar gum in the above salt type explosives, they have been utilized at pH levels of 6 and higher as set forth in US. Pat. No. 3,301,723.
• l have found that due to those high pH conditions various properties of the explosives product are impaired, particularly gel strength and stability, and stability of certain ingredients of the explosive.
• This invention is based on my discovery that gelled aqueous slurry salt explosives containing guar gum crosslinked with a chromium acetate(s) of a selected class can be prepared at significantly lower pH levels than heretofore, under which conditions the resulting explosive product exhibits markedly improved stability, water resistance, and viscosity characteristics.
• aqueous slurry salt type explosives containing guar gum crosslinked with a chromium acetate, as a gelation agent comprise calcium nitrate as at least part of the oxidizer salt component, and as said gelation agent guar gum crosslinked in the presence of at least part of said calcium nitrate at a pH of from about 4.5 to 5.4 with a chromium acetate of the group of chromium hydroxy diacetate, chromium triacetate, and mixtures thereof.
• a method for manufacture of a gelled aqueous salt slurry type explosive above described comprises incorporating calcium nitrate into said explosive as at least part of the oxidizer salt, and effecting the gelation by crosslinking said guar gum with said chromium acetate in the presence of at least part of said calcium nitrate within said pH range of from 4.5 to 5.4.
• the degree of the crosslinking can be varied over a broad range by regulating the amounts of guar gum and chromium acetate crosslinking agent incorporated into the formulation, and particularly when the amount of calcium nitrate present during the crosslinking reaction is at least about 5 percent, based on the weight of the explosive. Generally, based on the weight of the explosive, from about 0.1 to 1.5 percent guar gum is crosslinked with from about 0.01 to 0.5 percent of the chromium acetate.
• the consistency of the gelled explosive product is variable over a range of from difficultly pumpable to unpumpable; and when smaller proportions of the guar gum and chromium acetate crosslinking agent are utilized, the product consistency is easily varied from pumpable to readily pourable.
• Regulation of rate of the guar gum-chromium acetate cross-linking reaction can be increased by raising the crosslinking reaction temperature from ambient levels to as high as F. and higher; and the crosslinking rate can be lowered by lowering the reaction temperature from ambient temperature levels, and/or by the presence of acetate ion at any desired temperature level, preferably supplied by sodium acetate or acetic acid introduced into the crosslinking reaction system in an amount of from about 0.01 to 2.0 weight percent of the explosive.
• the invention due to the unique characteristics of the particular chromium acetates in respect of their behavior in the presence of calcium nitrate to accomplish the gelation at a pH of 5.4 and lower, provides for improved stability of the explosive from the standpoint of gel strength, gel stability, water resistance and im' proved viscosity characteristics; and it also provides for the use of chromium acetate-guar gum gelation systems in formulations which can only exhibit maximum stability of certain of the ingredients when the pH level of the explosive is markedly lower than 6.
• the invention is therefore particularly advantageously applied to those formulations containing metallic energizers such as aluminum, and those formulations in which density is controlled by the addition of gassing agents such as sodium nitrite, sodium carbonate, and others, which require pH levels not exceeding about 5 to 5.4 for maximum stability.
• Exemplary oxidizer salts utilized in the practice of the invention include inorganic oxidizer salts such as alkali metal and alkaline earth metal nitrates and perchlorates such as, for example, sodium nitrate, magnesium nitrate, potassium nitrate, barium nitrate, sodium perchlorate, ammonium perchlorate, calcium perchlorate and magnesium perchlorate; and organic salt components such as nitrogen based oxidizer fuel salts including hexamethylene-tetramine monoor di-nitrates, primary, secondary and tertiary alkyl, and alkanol, amine nitrates, generally containing one to four carbon atoms in each alkyl, or alkanol group, as for example, monomethylamine nitrate, dimethylamine nitrate, timethylamine nitrate, monoethylamine nitrate, diethylamine nitrate, tri
• Formulations contain nonexplosive fuels, as for exnitrate, and the like. 5 ample ethylene glycol, are advantageously employed in Particle size of the salt ingredients, which are norpractice of the invention.
• Nonsoluble fuels such as mally solid, is generally not critical.
• amground coal, powdered sulfur, fuel oil and other hydromonium nitrate can consist of prills such as used in fercarbons are also useful when suitably dispersed.
• the oxidizer salt component can be solely inor-
• the gelled explosive compositions of the invention ganic, or, except for the calcium nitrate, it can be solely are exemplified by those of the following formulations:
• organic or it can constitute a mixture of organic and inorganic salts either one of which can be in major proportion.
• the explosive compositions of the invention contain, as the now preferred oxidizer salt component, from about 5 to percent of the calcium nitrate, and additionally from about 10 to 80 percent ammonium nitrate alone or with a supplemental salt such as sodium nitrate.
• the calcium nitrate content of the oxidizer salt component is generally at least about 10 percent, and it can constitute all or any greater proportion of the oxidizer salt, as desired.
• the gelled explosives of the invention are detonatable in response to direction action of either a commercial No. 8 blasting cap or a conventional booster charge such as PETN (pentaerythritol tetranitrate), RDX (cyclotrimethylenetrinitramine), RDX (cyclotrimethylenetrinitramine), Pentolite (PETN-TNT), tetryl, Composition B (RDX-TNT), and the like, dependent on the particular sensitizer system.
• PETN penentaerythritol tetranitrate
• RDX cyclotrimethylenetrinitramine
• RDX cyclotrimethylenetrinitramine
• Pentolite PETN-TNT
• tetryl Composition B
• any of the various known sensitizer materials for inorganic oxidizer salt blasting compositions of the aqueous slurry type, above described, can be utilized as such, in the compositions of the invention.
• Exemplary of now preferred sensitizer components are smokeless powder as disclosed in U.S. Pat. No. 3,235,425, TNT and/or particulate aluminum as disclosed in U.S. Pat. No. 2,930,685, and ethylene glycol mononitrate as dis-
• the above formulations illustrate a chromium hydroxy diacetate/chromium triacetate mixture, and chromium triacetate alone, as crosslinking agents with guar gum in gelation system of the explosives of the invention.
• Examples 2 and 4 illustrate the use of an acetic acid-sodium acetate blend to lower the cross-linking rate;
• Example 1 illustrates a combination of low guar gum content and crosslinking agent for relative low consistency to form a pourable slurry product; and
• Examples 2 and 4 illustrate aluminum-containing formulations which, in contrast to similar formulations utilizing chromium salt/guar gum gelation systems of the prior art, are at substantially maximum stability.
• Example 2 Any suitable method can be utilized in the prepara tion of the explosive compositions of the invention.
• the explosive composition of Example 2 is formed in accordance with the following procedure:
• Ethylene oxide is reacted with aqueous nitric acid to form ethylene glycol mononitrate as described in U.S. Pat. No. 3,653,992, the resulting aqueous solution containing, on a weight basis, 36 percent ethylene glycol mononitrate, 24 percent ammonium nitrate, 30 percent water and 10 percent ethylene glycol by-product.
• the requisite amount of the solution is then admixed with the required amounts of the additional ingredients water, ammonium nitrate prills, calcium nitrate, zinc oxide, acetic acid and sodium acetate, and the resulting admixture is heated at T5 6 1 under 55:56am mixing conditions.
• guar gum as a dispersion in ethylene glycol
• ethylene glycol ethylene glycol
• a percent aqueous solution of the chromium acetate cross-linking agent- is added to, and uniformly mixed with, the above resulting ingredient mixture to form the final explosive ingredient mixture.
• the product ingredient mixture Prior to completion of the crosslinking reaction, the product ingredient mixture is packaged for storage during which time crosslinking is completed to form the final firm gel product.
• a gelled aqueous slurry salt type explosive containing guar gum crosslinked with a chromium acetate, as a gelation agent the improvement comprising calcium nitrate as at least part of the oxidizer salt component, and as said gelation agent guar gum crosslinked in the presence of at least part of said calcium nitrate at a pH of from about 4.5 to 5.4 with a chromium acetate of the group of chromium hydroxy diacetate, chromium triacetate, and mixtures thereof.
• a gelled explosive of claim 1 said explosive containing on a weight basis from 0.1 to 1.5 percent of said guar gum and from 0.01 to 0.5 percent of said chromium acetate crosslinked with said guar gum in the presence of at least 5 percent of said calcium nitrate at a pH of from 4.7 to 5.2.
• said calcium nitrate constituting at least 10 percent of said oxidizer salt component.
• a gelled explosive of claim 3 comprising from 5 to percent water, from 5 to 30 percent calcium ni- 6.
• a process of claim 8 wherein said chromium acetate is a mixture of chromium hydroxy diacetate and chromium triacetate.
• a process of claim 8 wherein said chromium acetate is chromium triacetate.

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Citations (2)

• 1973
  • 1973-03-26 US US00345161A patent/US3798091A/en not_active Expired - Lifetime
  • 1973-11-19 JP JP48130028A patent/JPS5145647B2/ja not_active Expired

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