Explosive and thermic compositions or charges – Structure or arrangement of component or product
Patent
1986-08-11
1987-06-30
Lechert, Jr., Stephen J.
Explosive and thermic compositions or charges
Structure or arrangement of component or product
149 21, 149 45, 149 92, 1491096, C06B 4500
Patent
active
046768491
DESCRIPTION:
BRIEF SUMMARY
This invention relates to explosive compositions, and more particularly to a method of manufacture of gas bubble-sensitized explosive compositions which are liquid when they are prepared.
Many explosive compositions are liquid during their manufacture; these include not only the aqueous emulsion and slurry explosives much used for blasting, but also various types of melts, wherein the manufacture is performed on a liquid phase but the end product is solid.
A widely-used means of reducing density and sensitizing explosive compositions is by the incorporation of gas bubbles. This has generally been achieved either by the addition of pre-encapsulated gas, for example, in the form of glass microballoons, or by the direct incorporation of gas. The latter method can be carried out by, for example, mechanical agitation, injection, bubbling the gas through the composition, or by in situ generation of gas by chemical means. The incorporation of gas bubbles in an aqueous emulsion by the in situ chemical generation of gas as a result of the decomposition of a foaming agent therein is described for example in U.S. Pat. Nos. 3,706,607, 3,711,345, 3,713,919, 3,770,522, 3,790,415 and 4,008,108.
In practice, pumping or mixing gas bubble-sensitized liquid explosive compositions can lead to bubble coalescence and bubble disengagement, and thus to reduced performance of the compositions. There have been suggested from time to time means for overcoming these disadvantages. For example, in the commercially very important emulsion explosives field, U.S. Pat. No. 4,008,108 describes a method in which pumping or mixing is finished before any substantial foaming (i.e. gas bubble formation) takes place. The partially foamed fine emulsion is then added to packages wherein the complete foaming takes place. This method works very well, but has the considerable commercial disadvantage that the packages must be left unsealed until foaming has finished (about 30 minutes). Moreover, the relatively slow gas generation necessitated by this method can lead to the formation of relatively large gas bubbles with diameters in excess of 200 micron. This in turn leads to lower performance.
We have now found a method for the manufacture of gas bubble-sensitized explosive compositions which provides surprisingly small gas bubbles and therefore enhanced explosive properties. We therefore provide, according to the present invention, a process for the preparation of a gas bubble-sensitized explosive composition which composition is liquid during the preparation, the process comprising the steps of group consisting of temperature and atmospheric pressure, and sufficient to maintain dissolved the major proportion of any gas present in the liquid; and composition a discontinuous gaseous phase.
The level of super-atmospheric pressure to which the composition is subjected is dependent to a considerable extent on the nature of the composition, its components and the capability of the mixed components to absorb or dissolve the gaseous material. The level will also depend on the nature of the gaseous material. The level may thus vary with differing gaseous materials. For example, the level of super-atmospheric pressure may suitably be low, such as for example 10 kilopascals, when the gaseous component is taken up easily by the remainder of the composition; yet again with certain gases in combination with some compositions it may be necessary to use pressure say up to 50,000 kilopascals. For many combinations of composition and gaseous component in common use we have found that pressures in the range from 100 to 10,000 kilopascals and usually in the range from 500 to 5,000 kilopascals are satisfactory and may be preferred for use in the process of the present invention. Preferably the pressure applied is sufficient to dissolve and/or maintain the major portion, and more preferably essentially all, of the gaseous phase in solution. In practice it has been found that with the compositions under pressure and the gaseous component in solution the liquid explosive c
REFERENCES:
patent: 3814694 (1974-06-01), Klager et al.
patent: 3886010 (1975-05-01), Thornley et al.
patent: 3995673 (1976-12-01), Grigaitis et al.
patent: 4008108 (1977-02-01), Chrisp
patent: 4303731 (1981-12-01), Torobin
patent: 4594118 (1986-06-01), Curtin et al.
Curtin David J.
Yates David E.
ICI Australia Limited
Lechert Jr. Stephen J.
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