CA2113945A1

CA2113945A1 - Low density explosives

Info

Publication number: CA2113945A1
Application number: CA002113945A
Authority: CA
Inventors: Fortunato Villamagna; Jeremy G. B. Smith; Lee M. Chung; Arun K. Chattopadhyay
Original assignee: Individual
Current assignee: Orica Explosives Technology Pty Ltd; ICI Explosives USA Inc
Priority date: 1993-02-18
Filing date: 1994-01-21
Publication date: 1994-08-19
Also published as: ZW2994A1; ZA94894B; MX9401290A

Abstract

ABSTRACT

Low Density Explosives A low density explosive material or explosive additive material is provided wherein, in a preferred embodiment, a heated melt or a saturated aqueous solution is mixed with a foaming agent to form a gas-in-liquid foam, and then cooled to effect solidification, or crystallization, and thus form a "gas-in-solid" foam having a density of less than 1.0 g/ml. The resultant material may be added to emulsion explosives as a sponge-like material to lower the density of the explosive, or may be dried and crushed to form a powder having a open and closed cell structure of low density.
The material itself, or the material in combination with other additives, may be used as an explosive or may be added to an explosive formulation to modify performance characteristics.

Description

Low Density Explosives Field of the Invention The present invention relates to a low density material, or structure, which can be used as an explosive ~er se, or can be used as an additive in conventional explosive materials.
,,,,"

Description of the Related Art -Semisolid colloidal dispersions of water-bearing 10 explosives (or blasting agents) are well known. These ;~
products typically comprise an oxidizing component, ~ ~ -usually predominantly ammonium nitrate, a fuel component, and water. These explosives are referred to in the art as slurry explosives (or as water gels), and as emulsion-type explosives.
Slurry explosives typically comprise a discontinuous ~
fuel phase which is dispersed in a continuous aqueous ~ `
solution of the oxidizer salt. Thickening agents are added to the aqueous phase in order to increase the vi~cosity of the explosive, or to effect gelation, and thus stabilize the structure of the explosive.
Emulsion explosives typically comprise a discontinuous aqueous oxidizer salt solution which is - ~ -~
dispersed in a continuous fuel phase. Emulsifying agents ;, ' I I i , ~ ' ! , , j , are generally added to the dispersion to stabilize the dispersion.
The addition of additives to both slurry and emulsion explosives to modify the performance of the explosive is similarly well known. These additives include, for example, the addition of TNT to the explosive to increase the strength and/or sensitivity of the explosive.
Of particular interest in the present invention is the addition of additives to create small voids within , " , ~,:

~:
~' 2ll3~'l3 the explosive, which voids can be used to control the density of the explosive, modify the detonation - -~
characteristics of the explosive, and/or increase the sensitivity of the explosive. Typical sensitized `-explosives were described, for example, by Cattermole et al. in U.S. Patent No. 3,674,578.
One method of addition of void~ in an explosive, is the addition of hollow glass microballons to an emulsion explosive. While this method provides a suitable means for the creation of voids within the explosive, the microballons are relatively expensive and can be difficult to handle due to their low bulk density.
Other products, similar to microballons, which contain one or a number of gas bubbles are also used in 15 the explosives art. These other products include, for -example, inorganic hollow micro-spheres made of glass, slrasu (Japanese volcanic ash), silicon sand, or sodium silicate and the like. These materials generally suffer from the same disadvantages as glass microballons.
Edamura et al. disclose, in U.S. Patent No.
4,543,137, the use of a gas-retaining agent such as those made from foamed polystyrene, foamed polyurethane and the like. The gas-retaining agents of Edamura et al. can have a rigid structure, similar to the inorganic microballons doscribed hereinabove, and can be brittle and sub~ect to breakage during handling, or can be made soft and spongy so as to be more resistant to inadvertent breakage during handling.
These soft and spongy gas-retaining agents are produced by foaming a foaming agent in a thermoplastic resin and allowing the thermoplastic resin to set and thus entrap gas within the resin structure.
However, this route of adding gas voids to the explosive requires the use of a thermoplastic resin which will only act as a fuel when the explosive is detonated.
In-situ generation of air or gas voids within the ;
explosive is an alternative method over the addition of '~ '""' .

2 ~

gas filled microballons, and typically comprises the -addition of a material which reacts in the explosive to generate a gas bubble. This gas bubble is entrained within the explosive by the viscous nature of the semisolid explosive. The generation of a gas void within the explosive by an in-situ chemical reaction is termed ;~
within the industry as chemical gassing, and is described in numerous patents, such as U.S. Patent Nos. 3,886,010 ~ -and 3,706,607. In these patents, the use of chemical ;~
gassing agents such as nitrites, weak acids, hydrazine and peroxides in slurry and/or emulsion explosives is described.
While chemical gassing is practiced in the industry, ~ --its use is limited because of the dlfficulty in controlling the reaction rate of the chemical gassing reaction. The degree of gassing may be insufficient, or may be excessively slow, under cold production temperatures.
A third route to introducing gas voids into an explosive is to mechanically agitate the explosive composition in order to entrain an occluded gas void within the explosive. This route has the disadvantage of ~
intensive mechanical agitation of a sensitized explosive, ~-and can be subject to poor long-term blasting stability as gas is slowly lost from the explosive.
A further route to the production of gas voids within an explosive explosive is described by Curtin and Yates in U.K.~ Patent Applic,atjiqn No. 2,179,035, wherein a gas bubble generating agent is added to the explosive prior to, or while, the explosive is subjected to super-atmospheric pressure to dissolve at least part of the gas present. The explosive is returned rapidly to atmospheric pressure and thus creates a fine discontinuous gaseous phase in the composition. However, 35 this production route requires the sensitized explosive ~`
to be prepared under pressure, and thus requires specialized equipment adapted to handle the pressurized `~

- . ' :;': ,:
: .

3 ~

explosive.
In our copending Canadian patent application No.
2,040,346, laid-open on October 13, 1992, an explosive composition is described wherein the explosive is 5 sensitized by the addition of a gas-in-liquid foam which -has been stabilized by the addition of a foaming agent to the foam. In our further copending~U.S. patent --;
application No. 07/866,023 filed April 9, 1992, a foam composition is described which can be prepared from a lo variety of materials, however, the foam is used as a ;
gas-in-liquid material. ~ -~
In light of the problems presented hereinabove, it is an ob~ect of the present invention to provide a low density material which acts as an explosive, and which 15 may be included in an emulsion, slurry, dry blasting ~ -agent, or dynamite, to lower the density of the explosive or modify its performance.

Summary of the Invention Accordingly, the present invention provides a structure comprised of a gas-in-solid foam characterized by a density of less than about 1.0 g/ml wherein said ~;
structure is comprised of an admixture of a single or plurality of foaming agents, and/or a carrier, together with a single or plurality of inorganic or organic materials, and combinations thereof and therebetween, which structure is liquid at foaming temperatures, and wherein said structure is characterized by being below ~ ;
the solid/liquid phase transition point of said materials ; ;
so that said materials are solid.
Various materials may be utilized in the practise of the present invention. Preferred materials include those which are solid at ambient temperatures of about 20-C but which will form a liguefied melt or a solution, preferably a saturated aqueous solution, at elevated temperatures. It is preferred that these elevated - - 2 l l 3 ~

temperatures fall within the range of 50OC to lOO C. ; -These materials can include urea, or salts such as sodium chloride, or sodium nitrate. Further preferred materials are various organic compounds which meet the criteria set ~ -out hereinabove. These materials may include compounds normally used as explosives on their own, such as trinitrotoluene (TNT), which co~pounds allow the blast properties of the explosives prepared in accordance with -the present invention to be modified, in addition having thair density lowered.
Preferred salts include salts which are traditionally known in the explosives industry as oxidizer salts. These salts include, for example, nitrates, chlorates, and perchlorates. Particularly preferred salts are alkali or alkali earth metal nitrate salts, which salts include, for example, sodium nitrate, potassium nitrate, and the like, or mixtures thereof. Most preferably, however, the salt is ammonium nitrate.
A preferred carrier is water, so as to form agueous ~-solutions of the inorganic and/or organic materials, where appropriate. However, the carrier may be any liquid substance, or substance which is compatible with the structure being prepared which is liquefiable at the foam Porming temperature.
The term "foam" in this document is used to describe a mass of gas bubbles which have been dispersed in a semi-saturated or saturated liquefied material or solution. The term "gas-in-solid foam" describes a foamed material wherein the material has solidified to a solid 30 structure when the material is cooled to a temperature ~ ~ `
below the solid/liquid phase transition point. This "gas-in-solid" foam is distinguished from a "gas-in-liquid" foam wherein the foam wall structure is maintained as a flexible liquid film.
Most of the volume of a foam is the gas phase, and typically, the gas phase may comprise at least 90% by volume for the lesser density foams. The bubbles formed ~ ~

.. . ~.. ~.

211 ~ ~3 -6- ~
' ' ', -:
..:
in the foam are essentially all closed cells, ie the gas ;
bubbles are surrounded by, and thus separated from each other, by thin, flexible films of the liquefied salt or compound melt or solution. However, as the foam cools, -5 the salt or compound solidifies as the temperature -decreases below the solid/liquid phase transition point of the salt or compound. The solidified salt or compound thus forms, within the flexible film, a rigid film around the gas bubbles. This rigid film has a number of cells which cells may be open or closed or some combination thereof.
Where the salt or compound forms crystals upon being cooled below the solid/liquid phase transition point, the solidification of the solid may be termed "crystallization". However, use of this term merely implies that the salt or compound has solidified at a temperature of less than the solid/liquid phase transition point.
In the case of ammonium nitrate, as an example of the 20 present invention, the cooled foam made from a saturated -aqueous solution, is a soft sponge-like material having crysta~s of ammonium nitrate present in the film ~ -surrounding the gas bubble. This ~gas-in-solid foam" ; -~ormed may be blended into an emulsion explosive, or the ~
25 like, to reduce the density of the emulsion. - -The foam may also be dried or freeze-dried to remove any remaining carrier liquid, such as water. This "dried"
~or more generally, solvent-free) material changes from the sponge-like material to become hard and brittle, and may be crushed and broken up into smaller fragments with open and closed cell structure, which can be added to, for example, a compatible explosive in a manner similar to the addition o~ glass microballons in the prior art. ~ -When broken, the powdered material has a collection of ` -35 open and closed cells, and still provides a density ~-lowering effect when blended into an e~ulsion explosive.
Alternatively, the dried material may exhibit 2 ~ 1 3 ~

explosive properties of its own, and may be used as a low density explosive.
The gas-in-solid foams of the present invention may be produced by mechanical agitation of the liquefied material ko entrain the gas voids within the liquid carrier. This operation is preferably conducted at temperatures just abo~e the solid/liquid phase transition point, or crystallization temperature, of the material in order that the foam can be cooled to effect lo solidification and/or crystallization, and thus effectively ~lock-in~ the foamed structure. A preferred temperature range for forming the foam is about 5 to lO-C
above the solid/liquid phase transition, or crystallization, te~perature.
Maintaining the foam at temperatures above the solid/liquid phase transition point, or crystallization point, of the salt or co~pound allows the liquid material to drain from the foam, and thus reduce the size of the film layer between gas bubbles. This is of use in the production of ultra-low density foams, but has the risk that the foam structure may disintegrate before ~--solidlfication, or crystallization, of the material, occurs.
In order to effectively lower the density of the 25 explosive, the gas-in-solid foams of the present ;~
invention preferably have a low density. In its role as a ~-density reducing agent, the gas-in-solid foam preferably -has a dansity of less, than 1.0 g~ml, more preferably below 0.5 g/ml and even more preferably below 0.2 g/ml. ~; ;
~he foams may also be produced by introducing or "sparging" a pressurized gas into a pressurized liquid component of the foam, and subsequently releasing the pressure on the system so as to create small gas bubbles within the liquid component. Again, the foam is cooled to effect crystallization, or solidification, and form the gas-in-solid foam.
Preferably, however, the foams of the present ~ , `: 2 ~ ~ 3 3 1 5 invention are prepared by a process for producing a gas-in-solid foam structure comprising heating a mixture of a foaming agent and/or a carrier, together with a single or plurality of inorganic or organic materials, and combinations thereof and therebetween, to a temperature above the solid/liquid phase transition point of said material, agitating said mixture to entrain gas bubbles within said mixture to form a gas-in-liquid foam;
and cooling said mixture to a temperature below said solid/liquid phase transition point to form a gas-in-solid foam. ~-The gas-in-solid foam structures of the present invention may be an explosive ~er se, or may be an non-explosive additive which may be added to various explosives in order to produce low density explosives.
Accordingly, the present invention also provides a low density explosive comprising: ~ `
i) an oil-based fuel phase, ;
ii) an oxidizer salt phase, and iii) a structure as described hereinabove.
Preferably, the explosive is an emulsion explosive comprising: ~
i) a base emulsion explosive comprising a continuous ;- ;
oil phase, a discontinuous aqueous oxidizer salt phase, 25 and an emulsifier: and -ii) a gas-in-solid foam structure as described `~
hereinabove.
The foams of the present invention are preferablyj ;
added to the explosive composition by a low shear mixing technique such as a static mixer, or a ribbon mixer.
During addition of the foam, the foam, either as a liqu~d-containinq sponge-like material or as a dried powder, is merely dispersed within the explosive composition. At this stage, there is generally no need for intense mechanical agitation to entrain additional gas voids within the explosive composition.
The presence of a gas bubble stabilizer in the ~
:',, :.'' : ~.. ....
., ."...

~ 1 ~3~5 ~
g emulsion may be beneficial during addition of the sponge-like material in order to aid gas retention.
The gas used to form the bubbles in the foams of the present invention may be any gas which is compatible with other components of the explosive. Preferably, the gas is air, carbon dioxide, or nitrogen, but any other gas could be used provided that the solubility of the gas in the liquid is controllable over the time and temperature range to which the sensitized explosive will be stored prior to use.
Control of the drainage rate before solidification, and thus control of the half-life of the gas-in-precursor liquid foam can be influenced, and effectively controlled, by the selection of the foaming agent. Any 15 suitable foaming agent may be added to the foam in order ~ ;~
to stabilize the liquid film around the bubble. ;~
The foaming agent stabilizes the film around the gas -~
bubbles in order to prevent them from bursting or ;
coalescing prior to solidification of the salt or compound as the material is cooled below the solid/liquid phase transition point. Typical foaming agents would include materials such as milk, egg, animal, vegetable, or fish proteins, such as for example, egg albumin or casein, or polysaccharides or starches, such as dextrin, 25 agar and guar, or the like, and any mixture thereof. The ;
foaming agent can also be a protein derivative or associated product such as phospholipids, lipoproteins, collagens, hyqrolyseq proteins,and globulins. Steroids may also be used as a foaming agent.
The foaming agent may also include water soluble or di8persible surfactants such as, for example, FC , FC-92 , ;
FC-100 , FC751 , which are all perfluorinated surfactants, or mixtures with other water soluble or water dispersible surfactants. Other foaming agents include, for example, derivatives of succinic anhydride, steryl octazylene phosphate and certain fatty alcohols. ;
As described hereinabove, the carrier used to prepare .

2 l 13~3 the foam is a material which is a liquid or a material which is a liquid at-foam forming temperatures. The carrier is also preferably compatible with the continuous phase of the explosive. The additives of the foaming solution can be dispersed or dissolved into the carrier.
The carrier may, however, take part in the detonation as a fuel, an oxidizer, a sensitizer,~or it may be inert.
The foam can be added to sensitize any suitable explosive material wherein gas voids are advantageous.
Explosive materials include, in particular, emulsion or slurry explosives, ANFO, low density ANFO, Heavy ANFO, and the like, but also includes propellants, high heave explosives, modified emulsions, cast explosives, nitro ;
ester based systems, and TNT, RDX or NG based systems. -These explosive compositions are generally well known to the skilled artisan, and are generally well described in ; ~-the prior art. -The explosive compositions of the present invention may also comprise additional additives to enhance or modify the properties of the explosive. The use of these additives is commonly known within the explosives industry, and include the solid dopes and sensitizers -commonly added to emulsions such as aluminum, ~`~
ferrosilicon, TNT (trinitrotoluene), AN (ammonium ;;~ ~
25 nitrate), MAN (methylaminenitrate), PETN (pentaerythritol ~;
tetranitrate) and the like. Further, additional sensitizing agents, such as for example, glass microballons, may also be used in combination with the , foams of the present invention. ;~

Examples The invention will now be described, by way of ;~
example only, by reference to the following examples. ' Ex--amDle 1 Various foams were prepared in order to demonstrate ~-2i139~

the ability to form a low density material. The foams were all prepared by the following procedure. An aqueous solution of a salt such as ammonium nitrate, sodium -nitrate, or sodium chloride, or a liquefied melt comprising, for example, ammonium nitrate and/or sodium nitrate, or urea, was heated in order to liquefy the material. A foaming agent, or mixture of foaming agents was added to the heated aqueous sol~tion, and the ~ ~-resultant mixture was rapidly agitated to produce a foam.
The foamed material was then cooled to allow the salt or compound to solidify as the temperature decreased below ` -the solid/liquid transition point, and thus lock-in the structure of the foam. The resultant foam was oven dried if water was present, and the final foam density was measured. The results of Example 1 are set out in Table 1. ' ~ ' ''~'''`'' ' ~,.'' '`,'~ '~''.

:,: ,: .:

...

2~ :~3~
-12- ~ :

Table 1: Foamed Material Exam~les Mixing Run No. Solution Temp. Foaming Dry Foam (-C) System Density :-q~ml :
1 81% AN 55 2% Albumin 19% Water 0.66%Guar T4072 0.283 97.34% Solution . ~
2 81% AN 55 2% Albumin 0.136 ~ -19% Water 98% Solution 3 81% AN 90 2% Albumin 19% Water 2% Dextrin No Foam .
96% Solution 4 81% AN 55 2% Albumin : ~:
19% Water 2% Dextrin 0.222 :~
96% Solution 75% AN 50 2% Albumin 25% Water 2% Sodium Alginate 0.245 .
96% Solution . .
20 6 81% AN 55 2% Albumin .. -19% Water 2% Agar 0.193 96% Solution ~ ~ :

7 81% AN 55 2% Albumin Poor .
19% Water 2% Acrylamide Foam `
96% Solution ~:

8 81% AN 55 3% FC 0.026 19% Water 97% Solution ~ .

9 81% AN 55 3% FC 100 . 19% Water 3% Methyl Cellulose 0.034 . :~
94% Solution i ;
81% AN ' '55 3% FC 100 ~ : ;.:;
19% Water L0% Dextrin 0.326 87% Solution 11 80% AN 55 3% FC 100 20% Water 10% Silica gel 0.0349 : :-87% Solution 12 80% AN 55 10% Texapon EX40 0.813 20% Water 90% Solution ':

2~334ff~fff -13 80% AN 55 15% Texapon EX40 0.475 20% Water 85% Solution ~ ~:
14 80% AN 55 22% Texapon EX40 0.182 -:~
20% Water 78% Solution , lS 64% AN 70 3% FC 100 ~ "~
13% SN 97% Solution 0.06 -~
23% Urea ~:~
16 50% AN 30 3% Caf~ein 50% Water 2% Sodium Dodecyl 0.03 Sulphate 95% Solution :~
17 55~ AN 30 O.S% Dodecyl Phenol :~
45% Water 1% Collagen -`~
1.5% Casein OfO5 . :
4% FC 100 93% Solution 18 55% AN 30 3% FC 751 ~::
45% Water 3% Casein 0.05 94% Solution 19 25% NaCl 75 2.7% Albumin 75% Water 8.8% Dextrin 0.166 ::
88.5% Solution 58.3% SN 71 2.7% Albumin 41.7% Water 8.8% Dextrin 0.148 . :~-88.5% Solution Notes~
AN - Ammonium nitrate SN = Sodium nitrate FC, FC 100, FC751 = Perfluorinated surfactants : * - Trade Mark ~.
~ .
:, f ~ f ; ~ . .

..
:~ ' ` ` '; !- ";` ' ff,:
., ~ , ....
'`.;' ,'.~ " "' ',.'"'.
" ;'' . . .,' . ' ,:' '' ~"
- ,: "'''',;: ,",' ':. ~"`' '::`

: ~`'`' :''' . -:
~ ,, ,", " ~,..

~" :"'-.~,'': :"

2~3~5 : :
-14- ~ -. ~:
.,'. '~
The gas-in-solid foams produced in Example 1 demonstrate that low density dried foams can be prepared from a variety of materials. The density of the foam is dependent upon, inter alia, the solution inqredients, the ~-5 foaming system selected, the temperature, and the -agitation time and effectiveness. A stable foam could not be prepared with Run No. 3 due to the high temperature used. However, a gas-in-solid foams was prepared using the exact same foaming system at a temperature of 55-C
(Run No. 4).

Exam~le 2 ~ `
A series of emulsion explosives were prepared which incorporated various gas-in-solid foam low density ~; `
materials as described in Example 1. The base emulsion explosive was prepared in accordance with known techniques by mixing a heated (90-C) aqueous solution of an oxidizer salt, such as ammonium nitrate and/or sodium ~
nitrate, with a heated oil fuel phase, optionally in the ` `
presence of an emulsifying agent. The base emulsion was cooled, and the low density explosive additive, was added. The resultant sensitized emulsion explosive was cooled to ambient temperature, and its detonation properties were measured.
:: -~
Run No . 22 ~ ;~
Base Emulsion: 93.9% AN/SN/Water (77% AN/11% SN/12% Water) 6.9% Oil Ph~ase 0.1% FC-740 Foam Additive: From Example 1, Run No. 4 Emulsion Explosive: 3.0 Kg of base emulsion was cooled to 75-C and blended with 452 g of Foam Additive. The ;
resultant explosive had a density of 1.16 g/ml.
Detonation Results: In a 2.5 inch (6.2 cm~ diameter cartridge, using a 20 g Pentolite primer, the velocity -,:,::

~1 ~ 3~5 of detonation ~VOD) was measured at 3.92 Km/sec.
Run No. 23 ~ . . . ~, .
Base Emulsion: 93% AN/Water (81% AN/19% Water) ;~
7% Oil Phase - ~
Foam Additive: From Example 1, Run No. 4 ~ ~ ;
Emulsion Explosive: Prepared aS described in Run No. ;
22. The resultant explosive had a density of l.lS g~ml. ;;~
Detonation Results: In a 3 inch (7.6 cm) diameter cartridge, using a 20 g Pentolite primer, the VOD was measured at 4.7 Km/sec. ~ ~--:
lS Example 2 clearly demonstrates that sensitized emulsion explosives can be prepared using the gas-in-solid foam additive of the present invention.
:; ~
Example 3 Since the gas-in-solid foamed nitrate additives contain a mixture of nitrate and organic material, they can act as explosives ~er se. Accordingly, a foamed AN
material was used to produce a variety of different explosives.
""`; ~ ' .
Run No~ 24 ~ `
~ .
1 Xg of the starting composition of Example 1, Run No. 4, was blended with 1 Kg of Ampal 60i atomized aluminum, and the resultant mixture was foamed. The ~-~
mixture was dried and had a final density of 0.136 g/ml. ;~
The mixture was packaged in a 1 inch (2.5 cm) diameter cartridge. When initiated with an EB cap, the mixture had a VOD of 1.83 Km/sec.
. ~ -. ~ . . : .

2 ~ 4 ~

~un No . 2 5 ~: .
1 Kg of the foamed AN from Example 1, Run No. 4, was blended with 65 g of Fuel Oil. The mixture was pacXaged in 2 inch (5 cm) diameter cartridges. When initiated with an EB cap, the mixture had a VOD of 2.0 Km/sec.

Run No. 26 1 Kg of the foamed AN from Example 1, Run No. 4, was blended with 1 Kg of AN prills. The mixture was packaged in a 1 inch (2.s cm) diameter cartridge. When initiated ;

10 with an EB cap, the mixture had a VOD of 1.8 Km/sec. - ~
~ .. ,i. .., ~, Exam~le 4 A series of emulsion explosives were prepared using ~ i the foamed sodium chloride material produced in Example 1, Run No. 19. The foamed material was added to an unsensitized commercial emulsion explosive, having an unsensitized density of 1.45 g/ml, in the ratio of 3000 grams of emulsion to 450 grams of foam. The explosives prepared were packaged in a variety of cartridge sizes, and the ability of the material to detonate was measure.
: . , Run No. 27 The mixture was packaged in a 3 inch (7.5 cm) diameter cartridge, and had a cartridged density of 1.25 g/ml. When initiated with a 40 gram primer, the sample detonated.

Run No. 28 The mixture was packaged in a 3 inch (7.5 cm) diameter cartridge, and had a cartridged density of 1.24 g/ml. When initiated with a 3 gram primer, the sample detonated.

F~

:- 2~3945 Run No. 29 The mixture was packaged in a 2 inch (5 cm) diameter cartridge, and had a cartridged density of 1.16 g/ml.
When initiated with an 80 gram primer, the sample detonated.

Run No. 30 The mixture was packaged in a 2 inch (5 cm) diameter cartridge, and had a density of 1.16 g/ml. When initiated with a 12 gram primer, the sample detonated.

Having described specific embodiments of the present invention, it will be understood that modifications -~
thereof may be suggested to those skilled in the art, and it is intended to cover all such modifications as fall ;~
within the scope of the appended claims. ~, ;

'''""'' ;'''`
:: :-`, ~ ,; ''.

''' `'`~ '''' '''`'''' :'.'` ' ",'.'. ,.,'',"',., ' ~' ' . i ','- ~, ,',:' i.'i'''

Claims

1. A structure comprised of a gas-in-solid foam characterized by a density of less than about 1.0 g/ml wherein said structure is comprises of an admixture of a single or plurality of foaming agents, and/or a carrier, together with a single or plurality of inorganic or organic materials, and combinations thereof and therebetween, which structure is liquid at foaming temperatures, and wherein said structure is characterized by being below the solid/liquid phase transition point of said materials so that said materials are solid.

2. A structure as claimed in Claim 1 wherein said structure is an explosive.

3. A structure as claimed in Claim 1 wherein said structure is combined with explosive materials characterized by having a density of greater than 1.0 g/ml.

4. A structure as claimed in Claim 1 wherein said material is alkali or alkali earth nitrate, chlorate, perchlorate, or mixture thereof.

5. A structure as claimed in Claim 4 wherein said material is a nitrate.

6. A structure as claimed in Claim 3 wherein said material is ammonium nitrate.

7. A structure as claimed in Claim 1 wherein said material is PETN or TNT.

8. A structure as claimed in Claim 1 having a density of less than 0.5 g/ml.

9. A structure as claimed in Claim 1 having a density of less than 0.2 g/ml.

10. A structure as claimed in Claim 1 wherein said foaming agent is a perfluorinated surfactant, a derivative of succinic anhydride, steryl octazylene phosphate, or a fatty alcohol.

11. A structure as claimed in Claim 1 wherein said carrier is water.

12. A structure as claimed in Claim 1 additionally comprising aluminum.

13. A process for producing a gas-in-solid foam structure comprising heating a mixture of a foaming agent and/or a carrier, together with a single or plurality of inorganic or organic materials, and combinations thereof and therebetween, to a temperature above the solid/liquid phase transition point of said material, agitating said mixture to entrain gas bubbles within said mixture to form a gas-in-liquid foam; and cooling said mixture to a temperature below said solid/liquid phase transition point to form a gas-in-solid foam.

14. A process as claimed in Claim 13 wherein said mixture is heated to a temperature of 5 to 10°C above said solid/liquid phase transition point.

15. A process as claimed in Claim 13 wherein said carrier is water.

16. A low density explosive comprising:
i) an oil-based fuel phase, ii) an oxidizer salt phase, and iii) a structure as claimed in Claim 1.

17. An emulsion explosive comprising:
i) a base emulsion explosive comprising a continuous oil phase, a discontinuous aqueous oxidizer salt phase, and an emulsifier; and ii) a structure as claimed in Claim 1.