Explosive and thermic compositions or charges – Structure or arrangement of component or product
Reexamination Certificate
2002-04-29
2004-03-09
Miller, Edward A. (Department: 3641)
Explosive and thermic compositions or charges
Structure or arrangement of component or product
C149S046000, C149S077000
Reexamination Certificate
active
06702909
ABSTRACT:
The present invention relates to a water-based explosive having physical and detonation properties similar to dynamite. More specifically it relates to a mixture of a water-in-oil emulsion phase with cast explosive particles and to a method of forming the same.
BACKGROUND
A “Holy Grail” in the modern explosives industry has been to find a water-based explosive to compete with dynamite. Water-based explosives generally are easier to manufacture than dynamites and do not emit fumes that can cause headaches as do dynamites. Unfortunately, water-based explosives do not perform as well as dynamites in certain hard rock and other demanding blasting applications.
A number of approaches and improvements in water-based explosives have been tried, see, for example, U.S. Pat. Nos. 3,770,522; 3,765,964; 4,310,364; 4,383,873; 4,453,989 and 5,074,939. Generally they do not measure up to dynamite in terms of high density, high detonation velocity, low critical diameter, low minimum booster, good air gap sensitivity, high detonation pressure and high energy, and these properties of dynamite are particularly important in certain blasting applications. One reason for the difference is that water-based explosives comprise composite mixtures of oxidizer and fuel ingredients whereas the sensitizing component in dynamites is a molecular explosive, in which the oxidizer and fuel molecules are covalently bound in the same molecule.
The most popular water-based explosives today are emulsion explosives, which comprise a continuous organic liquid fuel phase and a discontinuous oxidizer phase in the form of dispersed droplets of inorganic oxidizer solution. Typically an emulsifier is used to emulsify the solution into droplets. Emulsion explosives generally require air or gas bubbles (or microballoons) for sensitization purposes and thus have a significantly lower density and energy than dynamite. Thus a need exists for emulsion explosives that have a higher density and energy than heretofore available and that perform substantially like dynamite upon detonation. The present invention satisfies this need.
One approach to making emulsion explosives behave more like dynamite is to add to them a molecular explosive, such as PETN particles. Emulsion phases are most easily handled (and particles can more easily be added to and mixed uniformly throughout them) when hot, such as at their formulation temperatures (generally 70° C. or higher), and this is particularly the case if the emulsion phases contain waxes as a part of the fuel phase that increase in viscosity upon cooling. Hazards increase, however, when adding a molecular explosive to a hot emulsion phase. For example, PETN has a lowest DTA exotherm of about 150° C., which would be a safety concern if PETN particles were added to a hot emulsion. The present invention provides a particulate additive that can be added safely to a hot emulsion phase and that imparts higher density and energy to the resulting emulsion explosive.
A safety concern with dynamite or water-based explosives containing molecular explosives is that if left undetonated in a borehole, the molecular explosive component essentially will not degrade over time but will remain an explosive hazard. In seismic applications, for example, often there is considerable time between loading and shooting of the explosive charges. Further, undetonated products can be left inadvertently and by mistake in a borehole and thus the explosive hazard remains. This hazard also could occur if a defective detonator failed to initiate a charge. The explosives of the present invention will degrade by dissolving and/or dispersing with time in a borehole, particularly if in contact with groundwater, and thus will not leave a permanent explosive hazard.
SUMMARY
The emulsion explosives of the present invention are cap-sensitive and have a high energy, detonation velocity and pressure. They comprise a blend of a continuous emulsion phase and a discontinuous phase of cast particles. The emulsion phase is present in an amount by weight of the emulsion explosive of from about 25% to about 95%. The cast particles correspondingly are present in an amount of from about 5% to about 75%. The continuous emulsion phase comprises a continuous organic liquid fuel phase, a discontinuous inorganic oxidizer solution phase of ammonium nitrate and water, and an emulsifier. The cast particles comprise a mixture of from about 50% to about 80% anhydrous sodium perchlorate, from about 0% to about 10% water and from about 10% to about 40% diethylene glycol.
The method of the present invention involves mixing the cast particles throughout the emulsion phase while in their castable state and after or preferably before the particles have completely cured and reached their final sensitivity.
DETAILED DESCRIPTION
The emulsion explosives of the present invention comprise a blend of a water-in-oil emulsion phase with cast particles in a ratio by weight of emulsion phase to cast particles of from about 95:5 to about 25:75. Preferably, the ratio of emulsion phase to cast particles is from about 85:15 to about 40:60 and most preferably from about 75:25 to about 50:50. The ratio of emulsion phase to cast particles will depend on the desired application and on balancing the desired explosive properties with ease of mixing, cost and other factors. As the level of cast particles is increased, the ease of mixing is decreased and the cost is increased, but the detonation properties (such as velocity, energy and pressure) are improved. The emulsion phase comprises a continuous phase of organic liquid fuel, an emulsifier and a discontinuous phase or inorganic oxidizer salt solution. Other additives may be present as described below. The density of the emulsion explosives is from about 1.10 g/cc to about 1.60 g/cc and preferably is above 1.40 g/cc.
The immiscible organic fuel forming the continuous phase of the emulsion phase is present in an amount of from about 3% to about 12%, and preferably in an amount of from about 4% to about 8% by weight of the emulsion phase. The actual amount used can be varied depending upon the particular immiscible fuel(s) used and upon the presence of other fuels, if any. The immiscible organic fuels can be aliphatic, alicyclic, and/or aromatic and can be saturated and/or unsaturated, so long as they are liquid at the formulation temperature. Preferred fuels include tall oil, mineral oil, waxes, paraffin oils, benzene, toluene, xylenes, mixtures of liquid hydrocarbons generally referred to as petroleum distillates such as gasoline, kerosene and diesel fuels, and vegetable oils such as corn oil, cottonseed oil, peanut oil, and soybean oil. Particularly preferred liquid fuels are mineral oil, No. 2 fuel oil, paraffin waxes, microcrystalline waxes, and mixtures thereof. Aliphatic and aromatic nitro-compounds and chlorinated hydrocarbons also can be used. Mixtures of any of the above can be used.
Optionally, and in addition to the immiscible liquid organic fuel, solid or other liquid fuels or both can be employed in selected amounts. Examples of solid fuels which can be used are finely divided aluminum particles; finely divided carbonaceous materials such as gilsonite or coal; finely divided vegetable grain such as wheat; and sulfur. Miscible liquid fuels, also functioning as liquid extenders, are listed below. These additional solid and/or liquid fuels can be added generally in amounts ranging up to about 25% by weight. If desired, undissolved oxidizer salt can be added to the composition along with any solid or liquid fuels.
The inorganic oxidizer salt solution forming the discontinuous phase of the emulsion phase generally comprises inorganic oxidizer salt, in an amount from about 45% to about 95% by weight of the emulsion phase, and water and/or water-miscible organic liquids, in an amount of from about 0% to about 30%. The oxidizer salt preferably is primarily ammonium nitrate (AN), but other salts may be used in amounts up to about 50% of the total salts. The other oxidizer salts are selected from the group consisting of a
Hales Richard H.
Hansen Jared R.
Preston Scott B.
Dyno Nobel Inc.
Miller Edward A.
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