Chemical Foaming Of Water-bearing Explosives With N,n'-dimitrosopentamethylene-tetramine

Abstract

Making foamed semisolid colloidal dispersions of water-bearing blasting agents containing an inorganic oxidizing salt, e.g., ammonium nitrate, fuel, water and adding thereto the gas-generating material N,N'-dinitrosopentamethylenetetramine that foams and sensitizes the blasting agent.

Description

BACKGROUND OF THE INVENTION

Semisolid colloidal dispersions of water-bearing blasting agents are well known. These products typically comprise an oxidizing component, usually predominantly ammonium nitrate, a fuel component and water. More particularly, these blasting agents are referred to in the art as water gels or slurry explosives, and emulsion type blasting agents. The blasting agents commonly referred to as water gels contain, in addition to the above ingredients, a thickening agent that gels the composition, e.g., guar gum or polyacrylamides. In addition, the water gels may contain high explosives such as TNT, or metallic fuels such as aluminum that function not only as part of the fuel component of the blasting agent but also increase explosive strength. Representative water gels of the type disclosed hereinabove are more fully described in U.S. Pat. Nos. 3,153,606, 3,431,155 and 3,288,658. As indicated above, other water-bearing explosive compositions that are semisolid colloidal dispersions are known as emulsion type blasting agents. Emulsion type blasting agents contain, at least one oxidizing agent, water, an emulsifying agent and a fuel component that is a carbonaceous compound in water. The carbonaceous fuel used in the process for preparing these products is liquid during formation of the emulsion. The emulsifying agent generally forms a water-in-oil emulsion wherein oil is the continuous phase and water is the discontinuous phase of the emulsion. Representative water-bearing semisolid colloidal dispersions of emulsion type blasting agents are described in U.S. Pat. No. 3,447,978. Furthermore, these semisolid colloidal dispersions of waterbearing blasting agents, both the thickened water gel and emulsion type, have been prepared in such a manner that small gas bubbles are entrapped therein or they contain gas-entrapping material, e.g., microballoons. The inclusion of gas in the form of gas bubbles or in gas-entrapping material is known to regulate the strength of the blasting agent. Methods for preparing gas-containing water-bearing blasting agents include the mechanical incorporation of gas and in situ chemical generation of gas by the decomposition of certain compounds. Although these procedures have produced satisfactory products, there is a need for making foamed semisolid colloidal dispersions of water-bearing blasting agents by employing a gas-generating chemical compound that is simple to use; inexpensive; forms gas bubbles in the blasting agent within a short period of time that remain formed therein for extended periods of time; forms gas bubbles in the composition that are small, generally the majority of bubbles are not greater than about 100 micron diameter, preferably between 10 to 70 microns, for the most effective sensitivity; provides an effective control over the amount of gas introduced into the composition; and is applicable to water-bearing blasting agents, e.g., water gels, and emulsion type blasting agents.

SUMMARY OF THE INVENTION

This invention provides a process for preparing foamed semisolid colloidal dispersions of water-bearing blasting agents, especially water gels or thickened water-bearing explosives, and emulsion type blasting agents, which comprises mixing inorganic oxidizing salt, fuel and water, the improvement which comprises incorporating into the mix the gas-generating material N,N-dinitrosopentamethylenetetramine thereby foaming and sensitizing the blasting agent. When preparing a water gel, a thickening agent is added to the water-bearing explosive composition in order to thicken or gel the aqueous phase. When emulsion type blasting agents are prepared, an emulsifying agent and a liquid carbonaceous fuel are added to the water-bearing explosive during preparation in order to form an emulsion between the water and fuel. The amount of dinitrosopentamethylenetetramine added to the mix during preparation of the blasting agent is about 0.03 to 1 percent by weight based on the weight of the total composition.

DESCRIPTION OF PREFERRED EMBODIMENTS

The gas-generating material that is used in this process, i.e. N,N-dinitrosopentamethylenetetramine, decomposes and gives off gas at temperatures at which the blasting agent ingredients are formulated to produce a foamed product that is sensitized by small gas bubbles. The exact amount of gas-generating material used in the process varies and the specific amount employed depends upon the desired final density of the resulting product and the temperature of the formulation when the gas-generating agent is added thereto. Generally, amounts ranging about from 0.03 to 1 percent by weight, preferably about from 0.1 to 0.8 percent, are incorporated into the mix. The gas-generating agent is added to the composition at ordinary mixing temperatures, usually between 130.degree. to 180.degree.F. However, for optimum results, the gas-generating agent is added to the mix when the temperature of the mix is most favorable for decomposition of the foaming agent. Best results are obtained when the temperature of the mix during addition of N,N'-dinitrosopentamethylenetetramine to the mix is from about 140.degree. to 160.degree. F. Preferably, the gas-generating material N,N'-dinitrosopentamethylenetetramine is added to water gel type blasting agents after the mix has thickened, and to emulsion type blasting agents after the emulsion has formed, so that in each case the mix is sufficiently viscous to retain gas bubbles when the composition foams and small gas bubbles are formed therein.

The inorganic oxidizing salts used in this invention are those conventionally used in water-bearing blasting agents and include ammonium, alkali metal and alkaline earth metal nitrates and perchlorates as well as mixtures of two-or more such salts. Representative inorganic oxidizing salts are ammonium nitrate, sodium nitrate, potassium nitrate, magnesium nitrate, calcium nitrate, ammonium perchlorate, sodium perchlorate, potassium perchlorate and magnesium perchlorate. The amount of inorganic oxidizing salt use in the water-bearing blasting agents is from about 20 to about 75 percent by weight of the composition. Preferably, a mixture of inorganic nitrate salt are used of which at least about 45 percent by weight of the total composition is ammonium nitrate and of the order of 15 to 25 percent, preferably about 15 percent, based on the weight of the total composition, is sodium nitrate.

As mentioned above, the foamed semisolid colloidal dispersion of water-bearing blasting agents can contain a thickening agent to gel the composition, thus forming the well-known blasting agents known as water gels or slurry explosives. The amount of-thickening agent added regulates the consistency of the blasting agent and such thickeners are used in amounts ranging from about 0.2 to 5 percent. Representative thickeners include galactomannans such as guar and locust bean gum; gum arabic; starches and modified starches such as dextrins, polyvinyl alcohol; polyacrylamides; high molecular weight polyethylene oxides; or mixtures of two or more of the above thickening agents. Best results are obtained when guar gum or polyacrylamide is used as thickener with the gas-generating agent.

In addition, as mentioned above, this invention is applicable to the production of water and oil emulsion type water-bearing blasting agents. These compositions contain, in addition to inorganic oxidizing salt, water and fuel, an emulsifying agent. The amount of emulsifying agent used is from about 0.5 to 10 percent by weight, and preferably from about 1 to 2 percent. Larger quantities of emulsifying agent may be added since excess emulsifying agent merely serves as a supplemental fuel for the blasting agent. Generally, the emulsifying agents used are those that form water-in-oil emulsions, such as sorbitan fatty acid esters, e.g., sorbitan monolaurate, palmitate or oleate; polyoxyethylene sorbitol esters and long chain fatty acids and esters thereof, so that a water-in-oil emulsion of the blasting agent is formed. Especially good results are obtained when the emulsifying agent is formed. Especially a stearate salt, e.g., sodium stearate, alone or in combination with stearic acid. Other emulsifying agents include sodium oleate with or without oleic acid, dodecylbenzene sulfonic acid, tall oil amides such as the tall oil amide of tetraethylenepentamide, "EZ-Mul", manufactured by the Baroid Division of National Lead Co.

The fuels used in thickened water gel blasting agents include self-explosive fuels, nonexplosive fuels and metallic fuels as well as mixtures of the aforementioned types of fuels. Representative self-explosive fuels that can be used in the composition are organic nitrates, nitro compounds and nitramines such as trinitrotoluene, pentaerythritol tetranitrate, tetra-nitro-N-methylaniline, nitrostarch, explosive grade nitrocellulose, smokeless powder and mixtures thereof. Generally, the amount of self-explosive fuel used is from 10 to 40 percent by weight, based on the weight of the composition. Nonexplosive fuels such as certain nitro aromatic hydrocarbons, for example, mono- and dinitrobenzenes can be used, and sulfurous fuels including sulfur itself. Carbonaceous fuels such as finely-divided coal, hydrocarbons such as fuel oil and paraffin wax, can be added to the composition. Metallic fuels can also be used and these include light elements such as aluminum, magnesium, boron and silicon, both singly and in combination. Heavier metallic compounds and alloys including ferrophosphorus and ferrosilicon can be added to the mix. Blasting agents of the emulsion type wherein a water and oil emulsion is formed must contain carbonaceous fuel that is liquid during formation of the emulsion. The carbonaceous fuel is not soluble in water and generally forms the continuous phase of the emulsion so that the blasting agent is in the form of a water-in-oil emulsion. The carbonaceous fuel that is emulsified when used in the emulsion type blasting agents can include oil alone, a wax and oil, a wax and a polymeric material, or a wax and a polymeric modified oil component. The fuel used thus includes hydrocarbons such as paraffinic, olefinic and aromatic that are saturated or unsaturated. Waxes that can be used include paraffin wax and mineral waxes. Petroleum oil of varying viscosities can be used as the fuel, especially No. 2 fuel oil. Polymeric materials such as natural or synthetic rubber may be used as a carbonaceous fuel component. Preferably, the fuel comprises oil along. Generally, the amount of fuel used is from about 3 to 10 percent by weight. Optionally, the emulsion type blasting agents can contain supplementary fuels, as disclosed hereinabove, especially particulate metals, e.g. aluminum, and finely-divided coal. In general, the amount of fuel used in the blasting agents of the present invention is such that the oxygen balance of the blasting agent will be from -25 to +10 percent and preferably from -10 to +5 percent.

The amount of water used in the blasting agents of the thickened water gel and emulsion type is from 5 to 30 percent by weight, preferably about from 10 to 25 percent by weight water is used in preparing thickened water gels and emulsion type blasting agents.

Optionally, other ingredients can be incorporated in the blasting agents. For example, nitrogen-base salts can be added to the water-bearing blasting agents to increase their effectiveness. The nitrogen-base salt functions, among other things, as a fuel component and such salts that can be used in this invention are disclosed, for example, in U.S. Pat. No. 3,431,155. Preferably, the nitrogen-base salts used are monomethylammonium nitrate and ethylenediammonium dinitrate. Such salts can be added to the composition in amounts of from about 5 to 40 percent by weight. As is conventional in the preparation of thickened water gels, the composition can, and usually does, contain a crosslinking agent such as an alkali metal dichromate or a soluble antimony compound, e.g., potassium antimony tartrate, in amounts of from 0.001 to 1 percent by weight. Likewise, a crystal habit modifier for the inorganic oxidizing salt such as Petro AG, which is a derivative of naphthalene sulfonic acid salt, can also be added to water gel compositions, if desired. Generally, the procedure for making thickened water gels is as follows. The oxidizer salts and other water-soluble materials are mixed with water usually at temperatures between about 130.degree. to 180.degree.F to effect maximum solubility. Then the remaining ingredients, except thickener, crosslinking agent and gas-generating material, are added. The addition of these ingredients cools the mix. Subsequently, the mixture is agitated briefly and thickener added. Mixing is continued until thickening occurs and at temperatures of 130.degree. to 180.degree.F, preferably 140.degree. to 160.degree.F, the gas-generating material N,N'-dinitrosopentamethylenetetramine is added. The composition is mixed for about 30 seconds and then the crosslinking agent is added and a thickened foamed blasting agent sensitized with gas bubbles is obtained.

A procedure for making emulsion type blasting agents involves mixing the emulsifiable carbonaceous fuel and emulsifier at a temperature of about 130.degree. to 180.degree.F such that the fuel is liquified. Separately, the inorganic oxidizing salts and other water-soluble materials are dissolved in water at about 130.degree. to 180.degree.F, and the other materials (except for the liquid fuel/emulsifier mix) admixed therein. To this aqueous mixture is added the liquid fuel/emulsifier mix to form a water and oil emulsion. Preferably at this point in the procedure the temperature of the emulsion is usually between about 130.degree. to 180.degree.F, most preferably 140.degree. to 160.degree.F, or can be so regulated; the emulsion begins to thicken and the gas-generating agent is added to the thickened emulsion.

The following experiments further illustrate the invention in detail.

Example 1

Formulation Percent by Weight 1.1 1.2 Water 17.0 17.6 Ammonium nitrate 49.6 52.7 Sodium nitrate 16.0 16.6 Fuel 7.0(sugar) 2.5(fuel oil) Sulfur 5.0 5.1 Coal 3.0 3.0 Thickener (guar gum) b 0.9 1.0 Crystal modifier (Petro AG) 1.0 1.0 N,N' -dinitrosopentamethylene- 0.2 0.2 tetramine (60%) Crosslinking agent, sodium 0.3 0.3 dichromate solution (5%)

The ammonium nitrate, crystal modifier Petro AG (methyl naphthalene sulfonic acid) and the bulk of the sodium nitrate were dissolved in the water at about 160.degree.F. Subsequently the thickener, premixed with the sugar, when used, and the balance of the sodium nitrate were added to the oxidizer salt solution (155.degree.-160.degree.F). Finally the foaming agent N,N'-dinitroso- pentamethylenetetramine premixed with the sulfur and coal, was added to the above mixture at 140.degree.-150.degree.F. Fuel oil, when used, was admixed prior to thickener incorporation.

The specific gravity of the resulting foamed water gel blasting agent 1-1 containing small gas bubbles having diameters of about 10 to 100 microns was 1.1 and nine days later was still 1.1. The material had a detonation velocity of 4118 meters/second.

Foamed water gel blasting agent formulation 1-2 had a specific gravity of 1.1 and a velocity of 4118 meters/second. A replicate sample shot eight weeks later had a velocity of 4233 meters/second.

Example 2

Formulation Percent by Weight 2.1 2.2 Water 18.0 18.3 Ammonium nitrate 58.75 59.75 Sodium nitrate 15.0 14.9 Fuel oil 5.5 4.4 Sodium stearate 2.0 1.0 Stearic acid 0.9 N,N'-dinitrosopentamethylene- 0.75 0.75 tetramine (60%)

Ammonium nitrate, sodium nitrate and sodium stearate were mixed with the water at about 170.degree.F. The fuel oil (with the stearic acid, when used) was added thereto at 140.degree.-150.degree.F. When the mixture started to thicken the N,N'-dinitrosopentamethylenetetramine was added and mixing continued until a very thick mass formed. Small gas bubbles formed having diameters of about from 10 to 100 microns in the water-in-oil emulsion blasting agent.

Foamed emulsion formulation 2-1 had the following velocities at 40.degree.F:

diameter Velocity, meters/second 5 5640 4 5260 3 4010

Foamed emulsion blasting agent formulation 2--2 had a velocity of 5260 meters/second in 2-inch diameter at 40.degree.F confined in a steel pipe.

Example 3

Formulation Percent by Weight Water 0.2 Ammonium nitrate (75%) 76.3 Sodium nitrate 15.0 Fuel oil 5.0 Thickener, guar gum 1.0 Aluminum (pigment grade) 2.0 N,N' -dinitrosopentamethylene- 0.2 tetramine (60 %) Crosslinking agent, sodium 0.3 dichromate solution (5%)

The sodium nitrate was dissolved in a solution of ammonium nitrate at about 160.degree.F. The fuel oil and guar gum were premixed and added to the aqueous solution, and the slurry was agitated for about 2 minutes. Aluminum was then added and mixing continued for 1 more minute. The N,N-dinitrosopentamethylenetetramine was slurried in the water and added to the nitrate fuel oil mixture. After about another 30 seconds of mixing the crosslinking agent was added. The resultant water gel had a specific gravity of 1.12 and detonated at 4646 meters/second at 40.degree.F in a 6-inch pipe.

Claims

I claim:

1. In a process for preparing foamed semisolid colloidal dispersions of water-bearing blasting agents comprising mixing inorganic oxidizing salt, fuel and water, the improvement which comprises foaming and sensitizing the mix by incorporating into the mix the gas-generating material N,N'-dinitrosopentamethylenetetramine.

2. In a process for preparing foamed semisolid colloidal dispersions of water-bearing blasting agents comprising mixing inorganic oxidizing salt, fuel, thickener and water, the improvement which comprises foaming and sensitizing the mix by incorporating into the mix the gas-generating material N,N' -dinitrosopentamethylenetetramine.

3. The process of claim 2 wherein the amount of N,N'-dinitroso-pentamethylenetetramine added is about from 0.03 to 1 percent by weight.

4. The process of claim 2 wherein the amount of N,N'-dinitrosopentamethylenetetramine added is about from 0.1 to 0.8 by weight.

5. The process of claim 3 wherein the thickener is polyacrylamide.

6. The process of claim 3 wherein the thickener is guar gum.

7. The process of claim 3 wherein the inorganic oxidizing salt is ammonium nitrate.

8. The process of claim 3 wherein the mix is at a temperature of about from 140.degree. to 160.degree.F when the gas-generating material is added thereto.

9. The process of claim 3 wherein aluminum is added to the mix.

10. In a process for preparing foamed semisolid colloidal dispersions of water-bearing blasting agents comprising mixing inorganic oxidizing salt, liquid carbonaceous fuel, emulsifying agent and water, the improvement which comprises foaming and sensitizing the mix by incorporating into the mix the gas-generating material N,N' -dinitrosopentamethylenetetramine.

11. The process of claim 10 wherein the emulsifier is one that forms a water-in-oil emulsion.

12. The process of claim 11 wherein the amount of N,N' -dinitrosopentamethylenetetramine added is from 0.03 to 1.0 percent by weight.

13. The process of claim 11 wherein the amount of N,N' -dinitrosopentamethylenetetramine added is from 0.1 to 0.8 percent by weight.

14. The process of claim 12 wherein the carbonaceous fuel is fuel oil.

15. The process of claim 12 wherein the inorganic oxidizing salt is ammonium nitrate.

16. The process of claim 12 wherein the mix is at a temperature of about from 140.degree. to 160.degree.F when the gas-generating material is added thereto.

17. The process of claim 15 wherein the inorganic oxidizing salt contains sodium nitrate.

18. The process of claim 12 wherein the emulsifier is a stearate salt.