US3640784A - Blasting agents containing guar gum - Google Patents

Abstract

Granular water-resistant blasting compositions containing a water-soluble inorganic oxidizing agent, fuels, densifiers and guar gum.

Description

O United States Patent 1151 3,640,784

Yancik et al. 1451 Feb. 8, 1972 [54] BLASTING AGENTS CONTAINING [56] References Cited GUAR GUM UNITED STATES PATENTS [72] lnventors: Joseph J. Yaneik, Creve Coeur; Roy E.

5mm; Paul H. Rydhmd, both of St 3,432,371 3/1969 Grant ..149/44x FOREIGN PATENTS 0R APPLICATIONS z t. [73] 669,074 8/1963 Canada ..149/43 1 Mar-5, 1969 1,143,902 2/1969 Great Britain ..149/44 211 Appl. No.1 804,682

Primary Examiner-Leland A. Sebastian 52 u.s.c1. ..149/43,149/21, 149/42, ff f' Bmsk and 149/112, 149/113 1511 1111.121 ..C06b l/04,C06b 11/00, CO6bl9/04 ABSTRACT [58] meld ofsemhw Granular water-resistant blasting compositions containing a water-soluble inorganic oxidizing agent, fuels, densifiers and guar gum.

3 Claims, No Drawings "BLASTING AGENTS CONTAINING GUAR GUM This invention relates to dry; free-flowing granular blasting compositions and-particularly to water-resistant compositions containing a predominant proportion of a water-soluble inorganic oxidizing salt. v

' Armno'nium -nitrate has been used for many years asthe chief component in the preparation of blasting agents. Although ammonium nitrate and other water-soluble inorganic oxidizing salts serve very well in'the manufacture of efficientand economical blastingag'ents, they present a serious problem because they are readily soluble in water and very hygroscopic. It is therefore necessary to make some provision to eliminate their contact with water or, on the-other hand, to rriinimize the'efi'ect of water on them. Prior to the advent of thepresent invention; several methods have'been used to exclude water from explosive or blasting compositions based on water-soluble inorganic oxidizing salts, such as ammonium nitrate.= In severalinstances waterproof cartridges" have been succe'ssfullyemploye'dbut they materially increase the cost of the compositions and present some operational difficulties. Several attempts havealso been made to waterproof the compositions themselves. Such methods include the incorporation of nitrocellulose and liquid nitric esters, coating the watersolublesalts with waxes, resins, asphalts and other water repellantsfandthe incorporation of gel-forming water dispersible starches." More recently industry has resorted to explosives of the slurry type inwhich water is intentionally added to the composition. The slurry explosives are in essence a suspension of solids-including 'undissolved oxidizing salts in a saturated aqueous solution of the salt-.While'the slurry explosives have experienced some commercial success," they have one inherent and serious disadvantagethe presence of the required water normally 8 percent or more even when liquid extenders such as forrnamideare'used'detracts appreciably from their explosive strength per unit weight. Thus, all prior art compositions-utilizing water-soluble inorganic oxidizing salts have met 'withvarying'degrees of success but each has-had its shortcomings.

S Accordingly,'an object of this invention is to provide novel water-resistant blasting compositions overcoming the shortcomings of the prior art. A more specific object is to provide improved granular free-flowing water-resistant blasting compositions containing a predominant proportion of a watersoluble inorganic oxidizing salt.

' It has nowbeen found in accordance with the present-invention that=superior and advantageous-results are achieved by the preparation of-blasting-compositions containing within well-defined limits ammonium nitrate, a solid-densifying agent 'includingvferrophosphorus, ferrosilicon and ferromanganese,

a self-'complexing guar. gum, glycerine or ethylene glycol, a metallic sensitizer and source of high energy including alu- -rninum,- magnesium and alloys thereof, a water-resistant agent includingstearicacid -alkaline earth stearates and various types of waxes, and an oxide'or hydroxide 'ofan alkaline earth metal or ofzinc to serve as a temperature stabilizer. 'All components contribute to the'successful functioning of the compositions 'of the present inventionand are present'within welldefined limits. F The approximate ranges of each component that can be utilized in preparing the novel compositions of the present in- I vention are 54 to 95 percent ammonium nitrate, up to 10 percent ferropho'sphorus, ferrosilicon or ferromanganese, up to 5 percentethylene glycol, glycerine oraliphatic alcohols (C, *k to 5 percent s'elf-complexing guar gum, to 21 9% percent of aluminum-magnesium or alloys thereof, up to 2 percent stearit: acid, an alkali metal stearate or a wax, and up to 3 percent of'an oxide (Jr-hydroxide of an alkaline earth metal orzinc. in some instances minoramounts'-( up to about 2 percent) of fuel oil'can beadded to adjust the oxygen balance of the compositionsor to facilitate preparation of the compositions. The above-percentage range'sarebased on the weight of the composition. Likewise, throughout-the specification and claims 'all proportions are expressed in parts byweight orweight percent based on the total composition.

Although it is generally preferred to" use high-density ammonium nitrate of the type described, for example, in US. Pat: No. 3,030,179, more porous and low-density ammonium nitrate products can inmost instances be used withequal success. Likewise, the present invention is not limited to the physical form of the ammonium nitrate employed. Thus the nitrate can be prilled, granular or flaked-but optimum results have "been achieved with compositions containing com minuted ammonium nitrate varying in size with at least 60 percent of the particles having a major diameter-less than 1.68

mm. (12 mesh USS); In fact, commerciallyavailable prills which normally pass through a 12 mesh screen and are retained on a mesh screen-can constitute up to about 50 percent of the total ammonium nitrate in the present compositions with the remainder of the ammonium nitrate being comminuted'and-having theparticle size distribution indicated above. The-ammonium nitrate in the compositions of the present invention can bereplaced in whole or in partby nitrates, chlorates and perchlorates of the alkali metal and alkaline earth metal, and ammonium. Thus, suitable substituents include sodium'nitrate, calcium nitrate, magnesium nitrate, ammonium'chlorate, ammonium perchlorate and the like. For thesake of clarity and convenience the water-soluble inorganic oxidizing salt will be referred to hereinafter as ammonium nitrate.

The aluminum serves adual function and is present in two distinct forms. From about onefourth to 5 percent of the aluminum is in the'form of a powder having a-particle size sufficiently small to passthrough a 325'mesh screen. This finely divided aluminum serves primarily as a sensitizer and insures that the compositions will retain their sensitivity even in the presence of water. The remainder of the aluminum, that is, from about one-half to about 20 percent, is in the form of granules with aparticle size finer than 8 mesh or chopped foil and serves as a high-energy source. The foil has a thicknessof'about 0.05 mm. and an average major dimension of 2.4 mm. Both the chopped and granular materials have specific areas of at least about 0.2 sq. meters per gram and densities between 16 and 80 pounds per cubic foot. The aluminum'can be replaced by magnesium or aluminum-magnesium alloys.

The preferred solid densifier is ferrophosphorus. This material can however be replaced in whole or in part by ferrosilicon or ferromanganese. In any event, the solid densifier is in particulate form and mustbe sufficiently finely divided to pass throughan 80-mesh screen. Ferrophosphorus serves to increase the bulk density of the blastingcompositions and also as a fueland a serisitizer.

The guar gum used in accordance with the present invention must be of the self-complexing type. This material is commercially available under avariety of trade names and it is immaterial whether its self-complexing characteristics are inherent or are impartedby theaddition of one or more crosslinking-agents. It is only necessary that the gum be capable of forming astiff gel structure when exposedto water in' the must be carefully controlled to insure that the gum will crosslink so as to form a gel upon contact-with'water in contrast to merely forming a viscous flowable 'liquidsystem. It has been found'that' in compositions of the present invention the pH must be maintained-between 3.5' and 7.0.With more acidic systems the gums deteriorate and hydrolyze, whereas above pH 7 ammonia is released and the gums'fail to cross-link or form complexes. While satisfactory composition can be prepared between pH 3.5 and pH 7, it has been found that the optimum range is between pH 4.2'and pH 4.7. To maintain the required pH range it may be necessary to add a buffer. Various saltscan be used for this purpose but from the standpoint of convenience and economy it is preferred to use monoammonium-phosphate. The identity of the specific bufier is not critical but it is'only necessary that it buffers near the'pH- of the particular guar gum used and that it is compatible with the gum.

The temperature stabilizer such as magnesium hydroxide which is present in relatively small amounts serves to increase the high temperature storage stability of the present compositions by neutralizing any acid that may be liberated when the compositions of the present invention are stored at relatively high temperatures, that is from about 80 to about 110 F. Suitable temperature stabilizers include zinc oxide, calcium hydroxide, calcium oxide, barium hydroxide, and the like.

In preparing the blasting agents of the present invention it is preferred to mix the finely divided aluminum sensitizer with liquid densifier such as ethylene glycol or glycerine. The aluminum dust or powder is readily wetted by the glycol and forms therewith a thin suspension. The resultant suspension is then intimately mixed with the ammonium nitrate to form a substantially homogeneous admixture. The mixing of the aluminum dust with the glycol prevents the dust from becoming airborne and creating a potential hazard. The remaining components of the compositions are then added in any desired sequence and mixed until uniform. The compositions thus formed are dry, granular and free-flowing and have a built density of from 0.7 to 1.15. These materials are well adapted for loading into conventional cartridges which need not be waterproof. Since these materials are free-flowing and have excellent water resistance, it is more advantageous to charge them directly into bore holes. In this way the charge can conform exactly to the contour of the bore hole and eliminate any air pockets or gaps which would be present with cartridge loading. These compositions even when charged into a damp bore hole or one containing water will retain their sensitivity and detonation characteristics for a considerable period of time.

The present invention and the manner in which it achieves its advantageous results will be more readily understood by reference to the following specific illustrative embodiments thereof.

v EXAMPLE 1 About 0.5 part of -325 mesh aluminum dust was added to and suspended in about 1 part of ethylene glycol. This suspension of aluminum dust in the glycol was then added to about 79.5 parts of high-density ammonium nitrate prills that had been previously roll-crushed in accordance with the procedure of US. Pat. No. 3,291,659. The ammonium nitrate and the suspension were thoroughly mixed until the suspension had formed a substantially uniform coating on the ammonium nitrate particles. About 8 parts of chopped aluminum foil having an average major dimension of 0.6 mm. and a surface area of at least 0.2 sq. meters per gram, about 5 parts 80 mesh ferrophosphorus, about 2 parts self-complexing guar gum, about 1.15 parts of monoammonium phosphate, about 0.6 parts of magnesium hydroxide, and about 1 part of stearic acid were added to the ammonium nitrate slurry admixture. The sequence of addition of the various components is immaterial. During the addition the components were continuously mixed and mixing was continued until the composition was substantially uniform. The blasting composition thus obtained was cap-sensitive, that is, it was capable of being initiated with a No. 8 blasting cap. It was readily detonated with a V4 pound charge of 40 percent sernigelatin dynamite in contact with one end of a charge 1% inches in diameter and '7 feet long. When thus initiated the charge propagated throughout its entire length and had a detonation rate of approximately 10,000 ft. per second.

To illustrate the water resistance of this composition, cartridges 2% inches in diameter and 24 inches long were submerged under 10 feet of water for 24 hours each and then initiated with a as pound pentolite primer. This material which had been thoroughly wetted had a detonation rate of approximately 10,500 ft. per second unconfined.

EXAMPLE 2 About 30 axial inches of a nitrocarbonitrate composition made in accordance with the present invention and consisting of approximately 86.3% Ammonium nitrate 8% Aluminum granules 1% Ethylene glycol 1/2% Aluminum powder 2% Guar Gum (self-complexing) 1.2% Monoammonium phosphate 1% Stearic acid was placed under an 1 1 foot head of water in a 6-inch diameter pipe. The charge was maintained under the water for approximately 46 hours and then removed. A 1 pound cast pentolite booster was placed in contact with one end of the charge 7 and a 30 inch length of 150 gr. Primacord was positioned in contact with the other end of the charge. The booster was then initiated with a No. 6 electric blasting cap and the nitrocarbonitrate composition was completely detonated, as evidenced by the initiation of the Primacord by the nitrocarbonitrate composition.

For purposes of comparison, about 30 axial inches of a standard nitrocarbonitrate composition consisting of approximately percent ammonium nitrate, 6.4 percent aluminum granules, 10 percent ferrophosphorus and 3.6 percent fuel oil was placed under a 1% foot head of water in a 6-inch pipe. A 1 pound cast of pentolite booster was immediately placed at the nitrocarbonitrate water interface. The charge was left undisturbed for 3 hours and then inspected. About 18 inches of the nitrocarbonitrate column was no longer in a solid condition and the booster was completely surrounded by a mixture of water, ammonium nitrate solution, suspended aluminum and ferrophosphorus granules, and fuel oil. Upon initiation of the booster by a No 6 electric blasting cap the charge failed to denote.

EXAMPLE 3 Another nitrocarbonitrate composition in accordance with the present invention and consisting of approximately 40.4% Crushed ammonium nitrate 40.0% Pn'lled ammonium nitrate 2% Guar gum 8% Aluminum granules 5% Ferrophosphorus 1% Monoammonium phosphate 0.6% Magnesium hydroxide.

1% Ethylene glycol 0.5% Aluminum dust 1% Stearic acid 0.5% Fuel oil was charged into 42 bore holes, each 12 ft. long by 1% inches in diameter, by a conventional air placement technique. The condition of the holes varied considerably; nine of them were making from to 2 gallons of water per minute; eighth were as filled with standing water and the remainder were from damp to dry. After being charged, each hole was primed with a No. 6 electric blasting cap inserted into a stick of 40 percent sernigelatin dynamite, 24 inches long and having a diameter of 1% inches. The charges in each of the holes detonated completely regardless of the presence of running or standing water. The total powder factor was 0.535 pounds of explosive per ton and fragmentation from the blast was excellent. 7 7 n V A number of other compositions within the scope of the present invention were prepared, charged and initiated in like manner. The appropriate compositions and the sensitivity of these compositions both before and after being subjected to moisture are set forth below in tabular form.

TABLE Composition by weight percent Bulk mix Example Number AN Guar AL F021 MAP Mg(OH)2 Ethylene Al dust Steario Sensitivity Propagagnm glycol acid to N o. 8 E130 tion 1. 5 7 1. 15 0. 55 1 0. 1 1-DET Detonation.

2 8 5 1.1 0.56 l 0.5 1 I-DET D0. 2 8 5 1 1 0. 56 1 0. 5 1 1-DEI D0. 2 8 0 1. 1 0 0. 65 0. '25 1 11)El Do. 2 8 5 1. 1 0. 56 1 0. 5 1 1-DEI D0 1% 8 5. 5 1. 1 0 2 1. 0 0 1DET Do 2 8 5.5 1.1 0. 1 0.5 0 1-1)E'I D0.

In the above table, the ammonium nitrate (AN) in Examples 5 and 7 through was all roll-crushed in accordance with the procedure of US. Pat. No. 3,291,659; whereas the ammonium nitrate of Example 4 consisted of equal amounts of whole prills and crushed prills and the ratio of whole prills to crushed prills in Example 6 was 1:2.

In the above table, the tenn propagation indicates the ability of the charge to detonate after having been pneumatically loaded into a schedule 40 steel pipe 1% inches in diameter and 7 feet long which was initially filled with water. In each instance the column of nitrocarbonitrate was bottom-primed with semigelatin dynamite and initiated with a No. 8 electric blasting cap. By contrast, a conventional AN IFO composition consisting of 94 percent prilled ammonium nitrate and 6 percent fuel oil failed to propagate under the same conditions.

While the compositions of the present invention are particularly well suited forbulk loading, they are also readily adaptable for cartridge loading. In order to demonstrate this, car'- tridges 2% inches in diameter by 24 inches long were charged with a composition of the present invention consisting of about 81.5 percent of ammonium nitrate that had been rollcrushed in accordance with the procedure of US. Pat. No. 3,291,659, 2 percent guar gum, 8 percent aluminum granules, 5 percent ferrophosphorus, 1.15 percent monoammonium phosphate, 0.6 percent magnesium hydroxide, 1 ethylene glycol, 0.5 percent aluminum dust and 1 percent stearic acid. This charge had a packaged density of 1.17. For purposes of comparison, a more conventional composition containing about 80 percent roll-crushed ammonium nitrate, 6.4 percent aluminum, 10 percent ferrophosphorus and 3.6 percent fuel oil was charged into cartridges of the same type to provide a charge with the packing density of 1. 15. The loaded cartridges were punctured at both ends with a A-inch diameter hole and then soaked under a 10 ft. head of water for 24 hours.

In order to demonstrate the propagation capability of the compositions of the present invention, a vertical pipe 6 ft. long and 3 inches in diameter was closed at the bottom and filled with water. A dry cartridge charged with a composition of this invention was dropped into the pipe, a water wet cartridge placed on top of it and then another dry cartridge placed on top of it and then another dry cartridge. The dry cartridge was initiated with a rpound cast of pentolite booster. Upon initiation, all three cartridges detonated completely thus illustrating the ability of the charge to propagate a detonation wave whether the composition was wet or dry. When subjected to this same procedure, the conventional nitrocarbonitrate failed to propagate through the wet portion of the composition.

Thus it is evident that the particular compositions utilized in accordance with the present invention provide ammonium nitrate blasting agents that are not injuriously affected upon exposure to water or moisture.

While this invention has been described with respect to various specific examples and embodiments, it is understood that the invention is not limited thereto and that it can be variously practiced within the sco of the following claims.

The embodiments o the invention in which an exclusive property or privilege is claimed are defined as follows:

-monium phosphate; between about three-quarters and 2% percent aluminum, magnesium or alloys thereof. a predominant portion of the magnesium and aluminum being in the form of foil and the remainder being in the form of granules or finely divided foil; up to about 2 percent stearic acid, an alkali metal stearate or a wax; and between about 0 and about 3 percent of a oxide or hydroxide of an alkaline earth metal or zinc; the composition having a pH between 3.5 and 7.0.

2. A dry, free-flowing water-resistant blasting composition having a bulk density between about 0.7 and about 1.15 and comprising between about 54 and about 95 percent ammonium nitrate, 60 percent of which has a major diameter less than 1,680 microns; up to about 10 percent mesh ferrophosphorus; up to about 5 percent ethylene glycol; between about one-half and about 5 percent self-complexing guar gum; between about one-quarter and about 5 percent aluminum dust sufiiciently finely divided to pass through a 325 mesh screen; between about one-half and about 20 percent comminuted aluminum foil or granules having an average major dimension of 600 microns; up to about 2 percent stearic acid; up to about 3 percent magnesium hydroxide; and between about one-quarter and 2 percent monoammonium phosphate; the composition having a pH between 3.5 and 7.0.

3. A water-resistant blasting composition comprising a substantially homogeneous mixture of about 79.5 percent of highdensity roll-crushed ammonium nitrate prills, about 0.5 percent aluminum dust, about 8 percent finely divided aluminum foil, about 1 percent stearic acid, about 5 percent ferrophosphorus, about 2 percent self-complexing guar gum, about 1.2 percent monoammonium phosphate, about 0.6 percent magnesium hydroxide, and about 1 percent ethylene glycol.

Patent No. 5,640,784 Dat d February 8, 1972 Inventor(s) os ph J Yancik, et a1 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, line 59, delete "eighth" and substitute eight and delete "1/2" and substitute therefor 2/5 In the Table spanning Columns 5 and 6, under the heading "AN" relative to Example Number 6, delete "80.3" and substitute theIefOI' 801 8 "-0 Column 5, line 38, immediately after "1", insert Column 6, line 31, delete "2-l/2" and substitute therefor 21-1 2 Signed and sealed this 27th day of June 1972.

(SEAL) Attest'.

EDWARD MFLETCHER,JR ROBERT GOTTSCHALK I Attesting Officer Cozmnissioner of Patents FORM PO-1050 (10-69) USCOMM-DC 60376-P69 Q US4 GOVERNMENT PRINTING OFFICE: I959 0366-334 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent NO. 1 v Dated F r ry 197 Inventor(s) Joseph J. Yancik, et al It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, line 59, delete eighth" and substitute eight and delete "1/2 and substitute therefor 2/3 v In the Table spanning Columns 5 and 6, under the heading "AN" relative to Example Number 6, delete "80.3" and substitute therefor 80.8

Column 5, line 38, immediately after "1'', insert 75 Column 6, line 31, delete "2-1/2" and-substitute therefor 21-1 2 Signed and sealed this 27th day of June 1972.

(SEAL) Attest: I

EDWARD M.FLETCHER,JR. ROBERT GOITSCHALK Attesting Officer Commissioner of Patents FORM USCOMM-DC 60376-P69 U.S, GOVERNMENT PRINTING OFFICE I969 O356-334

Claims (2)

1. 2. A dry, free-flowing water-resistant blasting composition having a bulk density between about 0.7 and about 1.15 and comprising between about 54 and about 95 percent ammonium nitrate, 60 percent of which has a major diameter less than 1,680 microns; up to about 10 percent -80 mesh ferrophosphorus; up to about 5 percent ethylene glycol; between about one-half and about 5 percent self-complexing guar gum; between about one-quarter and about 5 percent aluminum dust sufficiently finely divided to pass through a 325 mesh screen; between about one-half and about 20 percent comminuted aluminum foil or granules having an average major dimension of 600 microns; up to about 2 percent stearic acid; up to about 3 percent magnesium hydroxide; and between about one-quarter and 2 percent monoammonium phosphate; the composition having a pH between 3.5 and 7.0.
2. 3. A water-resistant blasting composition comprising a substantially homogeneous mixture of about 79.5 percent of high-density roll-crushed ammonium nitrate prills, about 0.5 percent aluminum dust, about 8 percent finely divided aluminum foil, about 1 percent stearic acid, about 5 percent ferrophosphorus, about 2 percent self-complexing guar gum, about 1.2 percent monoammonium phosphate, about 0.6 percent magnesium hydroxide, and about 1 percent ethylene glycol.