AU2607688A

AU2607688A - Methods and compositions related to emulsified gassing agents for sensitizing explosive compositions

Info

Publication number: AU2607688A
Application number: AU26076/88A
Authority: AU
Inventors: John T. Day
Original assignee: Mining Services International Corp
Current assignee: Mining Services International Corp
Priority date: 1987-09-30
Filing date: 1988-09-28
Publication date: 1989-04-18
Also published as: ZW13188A1; WO1989002881A1

Description

METHODS AND COMPOSITIONS RELATED TO

EMULSIFIED GASSING AGENTS FOR SENSITIZING EXPLOSIVE COMPOSITIONS

BACKGROUND

The Field of the Invention

The present invention relates to methods and compositions for sensitizing emulsion explosive compositions. More particularly, the present invention is related to an emulsified gassing agent which produces a gas when mixed with selected emulsion blasting compositions, the gas then sensitizing the resulting mixture.

2. Related Applications

^"This application is a continuation-in-part application of copending application Serial No. 07/102,911, filed September 30, 1987, and entitled "Explosive Compositions," which application is incorporated herein by this reference.

3. Background of the Invention

Explosive compositions are widely used in various industries, including construction and mining. For example, in coal mining it is often the practice to drill an array of boreholes and subsequently fill those boreholes with explosives. The boreholes take on a particular pattern depending on the type of result desired. Once the boreholes are completed and filled with explosive compositions, the explosives are detonated, loosening the rock to be mined.^'

Similar procedures are used, in various types of construction. In constructing large projects such as roadways and large buildings, it is not unusual to encounter rock or other geological structures that are not easily moved by conventional equipment. In these instances explosives are often used to facilitate progress of the project. The use of explosives to^' accomplish such objectives is certainly not a new concept. Explosives such as trinitrotoluene (TNT) have been in use for many years. In recent years, however, improvements in the formulation of industrial and mining explosives have occurred. For example, explosives which are much less expensive than those traditionally used have now been developed. These include ANFO (ammonium nitrate-fuel oil), water gels and emulsion, all of which are based on nitrates such as ammonium nitrate. In addition, explosives which are less dangerous and more easily handled are now available.

Safety is naturally one of the serious concerns encountered in the handling of explosive compositions. The handling of explosive compositions presents unique problems. Once an explosive composition is fully prepared there is always the potential for accidental detonation of the explosive. Damage to both workers and property associated with a project may result. For these reasons, handling of explosives is generally subject to strict governmental and industry standards. ANFO explosives have been developed which overcome some of the problems encountered in the traditional art including, to a certain extent, the safety concerns. Several problems, however, remain with ANFO-based explosives. One problem which is often encountered in mining and construction is contact between the explosive and water. Since ANFO readily dissolves and will not properly detonate other explosives have been developed. Slurry explosives are generally aqueous based and do not always have good water resistance. Slurry explosives may also be prone to separation of the various components. In addition, slurry explosives often must be detonated by another fairly powerful explosive, such as TNT or pentolite.

In order to overcome some of the problems encountered with slurry explosives, emulsion explosive compositions have been developed. While oil-in-water emulsions have been the subject of experimentation and limited use, the most widely used emulsion explosive compositions are water-in-oil emulsions. Water-in-oil emulsions have been described for use in explosives for over 20 years. They consist essentially of an internal phase of an aqueous solution of oxidizers, with a continuous phase of oils, waxes and emulsifiers. Such emulsions, if appropriately formulated, can be explosive alone. Alternatively, they can be used in conjunction with solid oxidizers, sensitizers or other powerful explosives to form explosive compositions.

Water-in-oil emulsion explosives have several advantages. One advantage is that they are generally insensitive to mechanical shock. Thus, handling of these types of explosive compositions is not as dangerous as handling many traditional explosives. Furthermore, emulsion explosives of this type employ components such as wate _t fuel oil, and ammonium nitrate, that are not dangerous or difficult to handle prior to incorporation into an explosive composition.

Water-in-oil emulsion explosives are also relatively inexpensive. These emulsion compositions employ inexpensive ingredients (such as water, oil, ammonium nitrate, and emulsifying agents). Each of the primary components of this type of emulsion is readily available at relatively low cost.

As mentioned above, the water-in-oil emulsion explosive compositions are made of conventional and inexpensive materials which are not explosive. For this - A -

reason, the emulsions or its components may often be transported and handled without dealing with extensive governmental and industry standards which apply to explosive compositions. This is a distinct advantage of this type of composition.

One of the major problems in using emulsion explosive compositions is, however, that they are relatively insensitive. In order to detonate the explosive composition it is generally necessary to "sensitize" the emulsion.

Self-explosive sensitizers, either in dissolved form or in the form of a dispersed solid such as TNT, can be used to sensitize these emulsions. More commonly in commercial explosives, sensitization is achieved by the inclusion of a gas or voids in the explosive. Voids may be added in the form of gas trapping solids such as microspheres of glass or plastic, expanded polystyrene, or blown diatomaceous earth. As an alternative to the addition of mechanical density-reducing agents, emulsions can also be sensitized using chemical gassing agents.

Useful chemical gassing agents include compositions such as hydrogen peroxide and sodium nitrite which produce gas bubbles under certain chemical, catalyst, pH or temperature conditions.

Chemical gassing ^* agents are usually added to the emulsion-based explosive in the form of aqueous solutions of the chemical gassing agent. These agents commonly react with a co-reactant, usually hydrogen ions or manganese dioxide, which either exist or must be added to the internal aqueous phase of the emulsion. The rate of the gas liberating reaction generally increases with temperature and concentration of hydrogen ions or chemical catalysts in the internal aqueous phase of the emulsion. For example, the pH of the aqueous oxidizer phase can be adjusted to suitable levels with acetic acid before the emulsion is formed.

Uniform dispersion of the gassing solution in the emulsion is essential in order to effectively sensitize the emulsion. As was discussed above, however, water-in- oil emulsions have a desirable characteristic of high water resistance, while traditional gassing agents occur in aqueous solution. As a result, there rs an inherent resistance to mixing between the emulsion and the gassing composition. The result is that a vigorous mixing action is necessary to properly disperse an aqueous solution of gassing chemicals into an emulsion with an external oil phase. Even with such a mixing action, uniform distribution of the gassing agent is difficult to achieve. Thus, decreasing performance of the emulsion explosive composition is observed.

Accordingly, it would be a major advancement in the art to provide methods and compositions for more effectively employing emulsion explosive compositions. Similarly, it would be a major advancement in the art to provide methods and compositions for sensitizing and reducing density in such emulsion compositions. It would be a related advancement in the art to provide an improved composition for gas sensitizing emulsion explosives. It would be another advancement in the art to provide an emulsion gassing agent which was activated upon mixture with the emulsion explosive composition. Such methods and compositions are disclosed and claimed herein.

BRIEF SUMMARY AND OBJECTS OF THE INVENTION

The present invention is related to an emulsion composition and methods for its use in improving the blasting characteristics of emulsion explosive compositions. In particular, the emulsion of the present invention is formulated in such a manner that it provides desired sensitization and density reduction when added to conventional water-in-oil emulsion blasting compositions. When the emulsion of the present invention is added to the emulsion blasting composition, a gas is produced and is evenly dispersed as finely divided bubbles throughout the emulsion. The resulting gas bubbles provide both sensitivity and reduction of the density of the emulsion. The compositions and methods of the present invention provide methods whereby emulsion blasting compositions, which are not otherwise detonatable, can be be used alone, without the addition of ammonium nitrate prill, microballoons or other foreign substances as sensitizers. Because the present invention exists in emulsion form it is easily mixed with blasting emulsion compositions. In addition, the emulsion form provides waterproofing so that the- gassing agent is not dissolved, diluted or separated from the blasting emulsion when contacting water in a borehole or other blasting environment. The emulsion also provides completeness of reaction and intimate mixing between the various components. The emulsion of the present invention is stable and does not require the addition of costly antifreeze agents in cold environments.

The composition of the present invention is comprised of a water-in-oil emulsion containing a gassing agent. The gassing agent releases gas upon contact with the explosive emulsion. The gas may be released by an increase in temperature of the overall mixture, a change in pH, or other chemical reaction with the components of the explosive.

Various types of gassing agents may be used within the scope of the present invention. Gassing agents from alkali nitrite salts are preferred. One gassing agent of choice is sodium nitrite. Sodium nitrite is stable, soluble in water, and easy to handle and prepare into an emulsion. Other types of gassing agents are also within the scope of the present invention, including carbonates, bicarbonates, peroxides, and nitrites. However, agents which produce gases which are readily soluble (such a gas is CO2) are generally not as effective.

It will generally be desirable to include a companion salt in the gassing emulsion. Sodium nitrate is a preferred companion salt. Calcium, potassium or other metal nitrates have also been used with success. Other oxidizer salts such as alkali perchlorates can also be used. The functions of the companion salt are to take the place of some of the water in the aqueous phase, to adjust the density of the emulsion, and in some cases 'to adjust the oxygen balance of the entire system.

A carrier is also added to the water-in-oil emulsion. In most cases the carrier will be water. The amount of water in comparison with the remainder of the emulsion can be adjusted depending on the desired characteristics of the emulsion.

An additional desirable component of the gassing emulsion is a vehicle which produces the continuous phase of the emulsion. This vehicle will be an oil in character. Various emulsion carriers such as low cost No. 2 diesel oil, waste sump oils, waxes, mineral oils and the like can be used as vehicles so long as desirable characteristics of the final emulsion are provided.

Finally, it will generally be desirable to add a surfactant to the emulsion. The surfactant acts essentially as an emulsifying agent. Some acceptable surfactants include non-ionic, anionic, or cationic surface active agents such as sorbitan, fatty acid esters including sorbitan monooleate, sorbitan monolaurate, sorbitan palmitate, and sorbitan monostearate. Other agents will be discussed below.

The ranges of the various components may vary widely while still accomplishing the objectives of the invention. It will be appreciated that in order to achieve the objectives of the present invention it is only necessary to provide a water-in-oil emulsion having an integral gassing agent which releases a gas when mixed with the targeted explosive emulsion composition. In addition, the percentage of emulsified gassing agent in the final explosive mixture can vary widely from approximately 0.01% to approximately 50%.

Gassing agents preferably comprise from approximately 0.10% to approximately 50% of the final emulsified gassing agent. Concentrations of the companion salt may range from approximately 0% to approximately 45% of the emulsified gassing agent. The percentage of water is generally that which is required to bring the total composition to 100%. The vehicle typically comprises ^" from approximately 5% to approximately 50% of the emulsified gassing agent.

Finally, the surfactant may range from approximately 0.5% to approximately 10%.

It is, therefore, a primary object of the present invention to-- provide methods and compositions for increasing the effectiveness of emulsion explosive compositions.

It is a related object of the present invention to provide compositions and methods for sensitizing and adjusting density in such blasting emulsion compositions.

It is a further object of the present invention to provide improved composition for providing a gas within an emulsion blasting composition. It is also an object of the present invention to provide an emulsion which includes a gassing agent, which emulsion can be mixed with an emulsion blasting composition. These and other objects and advantages of the present invention will become apparent upon reading the following detailed description and appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is related to the preparation of an emulsified gassing agent for use in sensitizing emulsion explosive compositions, particularly water-in- oil emulsion compositions. The emulsion gassing agent and the emulsion explosive can be kept separate until a point in time immediately prior to introduction into a blasting site. Thus, it is possible to maintain the emulsion blasting composition as an insensitive composition prior to loading a borehole or the like. It will be appreciated that this greatly improves the safety and handling aspects of the composition.

It is also found that great advantage is derived by forming the gassing agent itself into a water-in-oil emulsion. The explosive emulsion • and the gassing emulsion, therefore, both have external oil phases and are compatible. Since they both have external oil phases they mix readily with relatively gentle mixing action. Uniform dispersion of the gassing emulsion within the main emulsion is much easier to achieve using the methods and compositions of the present invention. The emulsification of the gassing solution in this manner has several advantages. In order to minimize the amount of water added o the explosive, the gassing solution is often prepared in concentrated form. If too concentrated, such solutions may deposit crystals if the gassing chemical is a salt. It is well known in the art that the formation of small droplets as the internal phase of an emulsion prevents crystallization, even when the temperature of the emulsion drops well below the crystallization point of the solution. Thus, the use of a gassing emulsion allows the use of a highly concentrated gassing solution which will not crystallize when it forms the internal phase of the water-in-oil emulsion.

Alternatively, the gassing emulsion can include chemicals other than the gassing agent itself. For example, the internal phase of the gassing emulsion may include sodium nitrite and thiourea, at relatively high pH. Decomposition of the nitrite, which is aided by thiourea, will only commence when the gassing emulsion is dispersed in the explosive or blasting emulsion, the internal phase of which will have a lower pH. The gassing reaction is then initiated by the hydrogen ions provided by the explosive emulsion.

The gassing emulsion may also contain retardants or promoters depending on the extent and speed of gassing which is required. A suitable promoter for the liberation of gas by sodium nitrite is thiourea. Any base, such as sodium or potassium hydroxide, anhydrous ammonia, or hexamethylene-tetramine will act as a retardant by raising the pH and reducing the concentration of available hydrogen ions.

As mentioned above, the explosive emulsion will be comprised of a water-in-oil emulsion. Such emulsions are generally comprised of a carbonaceous fuel, including an eiαulsifiβr, constituting the continuous phase. An aqueous phase containing one or more oxidizer salts constitutes the discontinuous phase. The emulsion may also contain dispersed solid particulate oxidizers or fuels uniformly dispersed throughout the emulsion which form a continuous phase for the composition. Examples of suitable solid oxidizer particles are porous prill or crystalline ammonium nitrate, sodium nitrate, and limestone ammonium nitrate (which consists of a mixture of ammonium nitrate and calcium/magnesium carbonate). Examples of fuels include silicon, sulfur gilsonite, aluminum and wax.

Some oxidizer salt can also be included in the aqueous phase of gassing emulsion. The oxidizer salt may be any known in the art such as ammonium nitrate, calcium nitrate, sodium nitrate or mixtures thereof. Gassing emulsions containing ammonium nitrate and sodium nitrite in combination can be used but may not be very stable and will require careful pH control.

As mentioned briefly above, the gassing emulsion will contain a gassing agent. One preferred^' agent is sodium nitrite. Other gassing agents may include effective carbonates, bicarbonates, peroxides, and nitrites.

One preferred composition of the gassing emulsion includes a gassing^' agent, a companion salt, a vehicle, a surfactant, and a carrier such as water. One such system which is found to be useful has the following components in the following approximate percentages:

Representative Approximate

Function Chemical Composition Percentage

Gassing Agent Sodium Nitrite (NaN0₂) 20%

Companion Salt Sodium Nitrate (NaN0₃) 10%

Vehicle Oil (No. 2 Diesel) 19% Surfactant Sorbitan Monooleate 1%

Carrier Water 50%

As mentioned above, sodium nitrite is one gassing agent which is presently preferred. This gassing agent is crystalline yet fairly stable and soluble in water. It is also easy to handle and easy to add to solution in the emulsion. Sodium nitrite also readily generates gas when placed in a low pH environment such as an emulsion explosive.

The amount of gassing agent in the final mix is determined by the desired proportion of the emulsified gassing agent to the explosive composition. However, emulsified gassing agents with nitrite levels as low as

0.10% are used and still gas successfully. The upper limit is set by the solubility of the gassing agent.

Percentages of nitrite up to 50% are used with success.

In certain instances higher percentages may also be used.

The companion salt of choice is sodium nitrate.

Calcium or potassium nitrates have also been used with success. The major functions of the companion salt are to replace some of the water which adds only inert ingredients to the blasting emulsion, to adjust the density of the emulsified gassing agent for easier dispersion, to reduce gravimetric separation between the emulsions, and possibly to adjust the oxygen balance of the entire system.

Other salts will work in the system. Factors to be considered in selecting a salt are whether or not it is inert (which is to be avoided) and whether or not it is stable in the presence of the gassing agent. For example, ammonium nitrate is found to cause the sodium nitrite to react to form gas if the pH is not carefully controlled. However, potassium nitrate or sodium perchlorate have been found to be satisfactory.

The amount of companion salt can range from 0% to the solubility limit of the salt. High concentrations are often avoided in order to prevent the emulsified gassing agent from achieving a blasting agent classification. However, companion salt concentrations of up to 45% of the emulsified gassing agent have been used without problems related to emulsification or stability.

Water is the solvent of choice for the dissolution of salts, however, other solvents such as ethylene glycol or alcohols may be used as desired. The amount of water added is generally determined by the amount of other ingredients. The pH of the emulsified gassing agent in the system may be adjusted to prevent premature reaction of the gassing agent. Pretreatment of the water is, however, not normally necessary.

The vehicle forms the continuous phase of the emulsion and makes the emulsified gassing agent compatible with the blasting emulsion. The vehicle of choice is generally fuel oil (such as No. 2 diesel oil) because of its low cost and because of the resultant fluidity o.f the emulsified gassing agent. Other invert emulsion carriers can certainly be used as long as their 1 natural pH falls within the desired ranges. Such carriers include waxes, mineral oils, waste sump oils and the like, c The amount of vehicle determines the fluidity and stability of the emulsion. Emulsified gassing agents with oil levels of 5% to 25% have been prepared with success. Emulsions having oil content near the lower 0 levels are much more viscous, while those with oil levels over 20% may show oil separation. Oil levels of approximately 20% provide good fluidity and ease of pumping of the emulsified gassing agent, while retaining the desired stability.

The surfactant can be any of the accepted invert emulsion surfactants that do not cause the gassing agent to react. Suitable emulsifying agents found useful 0 herein are the water-in-oil type and include those derivable from sorbitol by esterification with removal of one molecule of water. Such sorbitan emulsifying agents may include sorbitan fatty acid esters such as sorbitan 5 monolaurate, sorbitan monooleate, sorbitan monopalmitate, sorbitan monostearate and sorbitan tristearate. The mono- and glycerides of fat-forming fatty acids are also _Q useful as water-in-oil type emulsifying agents.

Other water-in-oil type emulsifying agents which may be used include polyoxyethylene sorbitol esters such as the polyoxyethylene sorbitol beaswax derivative materials. Water-in-oil type emulsifying agents such as the isopropyl ester of lanolin fatty acids may also prove useful as may mixtures of higher molecular fatty alcohols and wax esters. Various other specific examples of water-in-oil type emulsifying agents agents include polyoxyethylene (4) lauryl ether, polyoxyethylene (2) oleyl ether, polyoxyethylene (2) stearyl ether, polyoxyalkylene oleyl/laurate, oleyl acid phosphate, substituted oxazolines and phosphate esters, to mention but a few. Mixtures of these various emulsifying agents as well as other water-in-oil type emulsifying agents may also prove useful.

The amount of surfactant may range from 0.5% to approximately 10% depending on the desired characteristics of the emulsion. Lower levels may tend to be less stable due to the lack of molecules at the oil/aqueous phase interface. However, lower levels of surfactant also reduce the overall cost of the emulsified gassing agent.

While the primary use of the emulsified gassing agent is to add a chemical gassing agent to a blasting composition, the emulsified gassing agent.- can also be prepared and used as a two component gassing system which adds both the acid and gassing agent with two separate emulsion compositions. That is, one emulsion could provide the gassing agent containing a nitrite, while another emulsion could provide the acid. Both emulsions would be added to the explosive composition. Such a system could be beneficial when the explosive emulsion was not previously prepared for gassing or where the components of the gassing system add instability to the blasting emulsion.

The emulsified gassing agent system can also be used to add a large variety of components to an emulsion or to adjust the characteristics of the emulsion. A partial list of such components and adjustments of characteristics follows.

Sensitizers such as powdered metals such as aluminum, self-explosives such as TNT, PETN, RDX, etc., other oxidizers such as alkali or ammonium perchlorates can be added.

Oxygen balancing of the existing emulsion can be accomplished because the emulsified gassing agent can be made with a wide range of oxygen balances.

Emulsion desensitization can also be provided for applications such as large borehole shooting and some underground applications. Adding an inert formulated emulsified gassing agent can desensitize a standard formulation emulsion for a given application.

The emulsion can be used for emulsion formulation modification. For example, if addition of a salt, water or oil to an existing emulsion lends desirable properties, the emulsified gassing agent system can be conveniently used to provide such a modification.

Viscosity adjustment can also be accomplished using the emulsified gassing agent. Viscosity is easily varied over a- wide range of viscosities from approximately 1,000 cP to over 100,000 cP. Addition of various amounts of viscosity adjusted emulsion can be used to adjust the final blasting emulsion viscosity.

As mentioned above, the emulsified gassing agent system of the present invention provides numerous advantages. One advantage is the fact that the system is waterproof. The emulsified gassing agent will not be removed from the blasting emulsion when loaded through water.

An additional advantage is the miscibility of the system. By being comprised of a similar continuous phase, the gassing agent is much more easily and thoroughly mixed with the blasting agent. In addition, the companion salt in the emulsified gassing agent may reduce the density difference between the gassing agent and the emulsion. This reduces one factor which would tend^" to cause separation of the gassing agent and the blasting emulsion in a water environment.

By choosing appropriate temperature, pH and mixing conditions, the emulsified gassing agent generates smaller bubbles than in a similar aqueous system. This desirable effect is likely due to a better distribution of the nitrite containing aqueous droplets throughout the blasting emulsion.

The emulsion forming the gassing agent is also much more stable and less likely to crystallize under low temperature conditions than is an aqueous form. This removes the need for costly antifreeze agents which are required in aqueous systems.

It is found that the emulsified gassing agent works " under a wide variety of parameters. For example, the pH range in the emulsified gassing agent is preferably between approximately 7.5 and approximately 12 showing no major effects on stability. Higher pH's, when achieved with buffering or by adding a basic salt such as hexamine can modify the gassing rate. By adding hexamine or a concentrated buffer system to the aqueous portion of the emulsified gassing agent, the reaction rate can be noticeably slowed.

The pH of the blasting emulsion can range from approximately 4.0 to approximately 0.5. Lower pH generally causes the reaction to occur faster. Higher pH values may produce a slower reaction. The pH of an aqueous phase of the blasting emulsion from approximately

2.0 to approximately 2.3 is considered to be optimum for many uses. In addition, a reaction time from approximately 3 to approximately 10 minutes (depending on temperature) achieves the required gassing in most applications.

The rate of reaction can also vary over a wide temperature range. Temperatures in the range of from approximately -10°C to approximately 75°C produce desirable results. The rate of reaction is affected as would normally be expected applying chemical kinetics. It is found that the optimum temperature is generally from approximately 30°C to approximately 40°C, while mixing temperatures are best in the range of approximately 20°C to approximately 40°C.

Thus, it can be seen that the emulsified gassing agent of the present invention provides great flexibility. Various agents can be mixed with emulsion blasting agents to optimize the resulting performance of the blasting agent. In addition, reaction parameters can be carefully controlled to produce precise results.

EXAMPLES The following examples are given to illustrate the general scope of the present invention, but these examples are not intended to limit the scope of the invention.

Example 1

An emulsified gassing agent was prepared by mixing the following ingredients:

Ingredients Percentage

Sodium Nitrite 20%

Sodium Nitrate 10%

Water 50%

No. 2 Diesel Oil 19%

Sorbitan Monooleate 1% The emulsion was made in the conventional manner by dissolving the sodium nitrite and sodium nitrate in the water to form an aqueous phase. This aqueous phase was added by vigorous stirring to the oil, to which had been added the emulsifier, until an emulsion was formed.

The thus formed gassing emulsion composition was then added with stirring to a conventional water-in-oil explosive composition at a rate of 0.6 cc per 1,000 grams. A uniform distribution of the emulsified gassing agent through the explosive emulsion was easily achieved. Gas bubbles of uniform size and distribution were observed in the resulting matrix.

Example 2 An emulsified gassing composition was made using the following ingredients:

Ingredient Parts

Calcium Nitrate 60

Sodium Nitrate 15

Sodium Nitrite 0.54

Water 24.46 This aqueous phase was then mixed with the following ingredients:

Ingredient Parts

Oil 7

Sorbitan Monooleate 2 The thus formed gassing emulsion composition was added with stirring to a conventional water-in-oil explosive emulsion at a rate of 12% by mass. A uniform distribution of the gassing emulsion through the explosive emulsion was easily achieved and gas bubbles of uniform size and distribution were observed in the resulting matrix.

Example 3 The emulsified gassing agent of Example 1 was modified to reduce the rate of the gassing reaction. To

100 grams of the emulsion of Example 1 was added 100 grams of a solution consisting of 43% water and 57% hexamine (hexamethylene tetramine). This basic solution was readily incorporated into the internal phase of the gassing emulsion of Example 1 to form a new emulsified gassing agent containing basic hexamine as a gassing rate retardant.

When added to a test explosive emulsion of pH 3.5 this gassing emulsion composition caused gassing at a significantly slower rate than that achieved with the emulsion of Example 1. The expected reduction in density was nevertheless achieved with the uniform distribution of' gas bubbles. Example 4

An emulsified gassing agent is prepared according to the method of Example 1. The various ingredients and their percentages are as follows:

Ingredient Percentage

Sodium Nitrite 25%

Oil 25% Sorbitan Monooleate 7%

Water 43%

The emulsified gassing agent prepared according to the above specifications produces an acceptable gassing agent for addition to water-in-oil explosive compositions.

Example 5 An emulsified gassing agent is prepared according to the method of Example 1. The various ingredients and their percentages are as follows:

Ingredient Percentage

Sodium Nitrite 10%

Sodium Nitrate 45%

Oil 5%

Sorbitan Monooleate 0.5%

Water 39.5%

The emulsified gassing agent prepared according to the above specifications produces an acceptable gassing agent for addition to water-in-oil explosive compositions. Example 6 An emulsified gassing agent is prepared according to the method of Example 1. The various ingredients and their percentages are as follows:

Ingredient Percentage

Sodium Nitrite 15% Sodium Nitrate 25%

Oil 20%

Sorbitan Monooleate 4%

Water 36% The emulsified gassing agent prepared according to the above specifications produces an acceptable gassing agent for addition to water-in-oil explosive compositions.

Example 7 An emulsified gassing agent is prepared using the methods of Example 1 and the ingredients of Example 1, with the exception that potassium nitrite is substituted for sodium nitrite.

This emulsified gassing agent is acceptable for adding to a water-in-oil explosive composition to produce gas.

Example 8

An emulsified gassing agent is prepared using the methods of Example 1 and the ingredients of Example 1, with the exception that calcium nitrite is substituted for sodium nitrite.

Example 9 An emulsified gassing agent is prepared using the methods of Example 1 and the ingredients of Example 1, with the exception that barium nitrite is substituted for sodium nitrite. This emulsified gassing agent is acceptable for adding to a water-in-oil explosive composition to produce gas.

Example 10 An emulsified gassing agent is prepared using the methods of Example 1 and the ingredients of Example 1, with the exception that hydrogen peroxide is substituted for sodium nitrite and an effective quantity of manganese dioxide is added to the blasting emulsion.

This emulsified gassing agent is acceptable for adding to a water-in-oil explosive composition to produce gas. Summary

It can be seen, therefore, that the present invention accomplishes each of the objects listed above. The present invention provides methods and compositions for increasing the effectiveness of emulsion explosive compositions. The emulsified gassing agent of the present invention is usable for sensitizing and adjusting density in such emulsion blasting compositions. This is done largely through providing a gas which is generated when the emulsified gassing agent is combined with the emulsion blasting composition. it will be appreciated that this invention provides several advantages. For example, the sensitization can be added at the last minute before the emulsion is put into place for blasting. ^' Furthermore, the water-in-oil emulsified gassing agent allows easy mixing with the blasting emulsions. Thus, complete distribution of the gassing' agent within the blasting emulsion is accomplished. We claim:

Claims

1. A composition for sensitizing emulsion explosives comprising an emulsion containing at least one material which generates a gas when the composition is added to selected emulsion explosives.

2. A composition for sensitizing emulsion explosives as defined in claim 1 wherein said emulsion explosive is a water-in-oil emulsion.

3. A composition for sensitizing emulsion explosives as defined in claim 1 wherein the sensitizing composition is a water-in-oil emulsion.

4. A composition for sensitizing emulsion explosives as defined in claim 1 wherein said material which generates a gas is a nitrite.

5. A composition for sensitizing emulsion explosives as defined in claim 4 wherein^" said nitrite is sodium nitrite.

6. A composition for sensitizing emulsion explosives as defined in claim 1 wherein said material which generates a gas is selected from the group consisting of carbonates, bicarbonates, and peroxides.

7. A composition for sensitizing emulsion explosives as defined in claim 4 wherein the aqueous phase of the water-in-oil emulsion includes an effective quantity of thiourea.

8. A composition for sensitizing emulsion explosives as defined in claim 3 wherein the water-in-oil emulsion further comprises water, a companion salt to the gas generating material, at least one vehicle, and at least one surfactant.

9. A composition for sensitizing emulsion explosives as defined in claim 8 wherein the vehicle comprises an oil.

10. A composition for sensitizing emulsion explosives as defined in claim 9 wherein the vehicle comprises diesel oil.

11. A composition for sensitizing emulsion explosives as defined in claim 8 wherein the gas generating material comprises sodium nitrite and the companion salt comprises sodium nitrate.

12. A gas generating water-in-oil emulsion for use in sensitizing emulsion explosives comprising at least one gas generating material, water, at least one vehicle and at least one surfactant.

13. A gas generating water-in-oil emulsion for use in sensitizing emulsion explosives as defined in claim 12 further comprising at least one companion salt to the gas generating material.

14. A gas generating water-in-oil emulsion for use in sensitizing emulsion explosives as defined in claim 12 comprising from approximately 0.1% to approximately 50% gas generating material.

15. A gas generating water-in-oil emulsion for use in sensitizing emulsion explosives as defined in claim 14 comprising from approximately 5% to approximately 25% vehicle.

16. A gas generating water-in-oil emulsion for use in sensitizing emulsion explosives as defined in claim 14 comprising from approximately 0.5% to approximately 10% surfactant.

17. A gas generating water-in-oil emulsion for use in sensitizing emulsion explosives as defined in claim 13 comprising 45% or less companion salt.

18. A water-in-oil emulsion for providing gas within an explosive composition comprising from approximately 0.1% to approximately 50% gas generating material, up to approximately 45% of at least one companion salt to the gas generating material, from approximately 5% to approximately 25% vehicle, from approximately 0.5% to approximately 10% surfactant, with the remainder of the composition comprising water.

^• 19. A water-in-oil emulsion for providing a gas within an explosive composition as defined in claim 18 wherein the gas generating material comprises sodium nitrite.

20. A water-in-oil emulsion for providing a gas within an explosive composition as defined in claim 19 wherein the gas generating material is selected from the group consisting of potassium nitrite, calcium nitrite and ÷ ,b_ari•um ni.tri.te.

21. A water-in-oil emulsion for providing a gas within an explosive composition as defined in claim 18 wherein the gas generating material is selected from the group consisting of carbonates, bicarbonates, peroxides and of sodium and potassium.

22. A water-in-oil emulsion for providing a gas within an explosive composition as defined in claim 18 wherein the companion salt is selected from the group consisting of sodium nitrate, calcium nitrate and potassium nitrate.

23. A water-in-oil emulsion for providing a gas within an explosive composition as defined in claim 18 wherein the vehicle is diesel oil. "

24. A gas producing emulsion composition comprising an aqueous phase having at least one gas producing material, at least one companion salt, and water combined with an oil phase having at least one oil and at least one surfactant, said emulsion ^"producing a gas when combined with an explosive water-in-oil emulsion at pH _L , below approximately 4.0.

25. A gas producing emulsion composition as defined in claim 24 wherein the gas generating material is a nitrite.

26. A method for producing a sensitized explosive composition comprising the steps of:

(a) obtaining an explosive composition comprising an emulsion;

(b) obtaining a gas producing emulsion, which emulsion produces a gas when combined with the explosive composition; and

(c) combining the explosive composition with the gas producing emulsion to produce a gas sensitized explosive composition.

27. A method for producing a sensitized explosive composition as defined in claim 26 wherein the explosive composition comprises a water-in-oil emulsion.

28. A method for producing a sensitized explosive composition as defined in claim 26 wherein the explosive composition further comprises a particulate material.

29. A method for producing a sensitized explosive composition as defined in claim 26 wherein the gas producing emulsion comprises a water-in-oil emulsion.

30. A method for producing a sensitized explosive composition as defined in claim 26 wherein the gas producing emulsion contains a gas generating material.

31. A method for producing a sensitized explosive composition as defined in claim 29 wherein the particulate material is ammonium nitrate.

32. A method for producing a sensitized explosive composition as defined in claim 29 wherein the particulate is selected from the group consisting of sodium nitrate, aluminum, and limestone ammonium nitrate.

33. A method for producing a sensitized explosive composition as defined in claim 30 wherein the gas generating material releases a gas when placed in contact with available hydrogen ions.

34. A method for producing a sensitized explosive composition as defined in claim 33 wherein the explosive composition has a pH from approximately 0.5 to approximately 4.0.

35. A method for producing a sensitized explosive composition as defined in claim 33 wherein the explosive . . composition has a pH of from approximately 2.0 to approximately 2.3. 1 36. A method for producing a sensitized explosive composition as defined in claim 26 wherein the gas producing emulsion comprises from approximately 0.1% to

5 approximately 25% gas generating material, up to approximately 45% of at least one companion salt to the gas generating material, from approximately 5% to approximately 25% vehicle, from approximately 0.5% to approximately 10% surfactant, with the remainder of the composition comprising water.

37. A method for sensitizing an emulsion explosive

15 composition comprising the step of adding a gas producing emulsion to the explosive composition, which gas producing emulsion is formulated such that a gas is

2o released when it is mixed with the explosive composition.

38. A method for sensitizing an emulsion explosive 25 composition as defined in claim 37 wherein said emulsion explosive composition is a water-in-oil emulsion.

39. A method for sensitizing an emulsion explosive

30 f. composition as defined in claim 38 wherein said gas producing emulsion is a water-in-oil emulsion.

<

35

40. A method for sensitizing an emulsion explosive composition comprising the steps of:

(a) obtaining a water-in-oil emulsion explosive composition;

(b) obtaining a water-in-oil emulsion for providing gas within an explosive composition comprising from approximately 0.1% to approximately 25% gas generating material, up to approximately 45%

. of at least one companion salt to the gas generating material, from approximately 5% to approximately 25% vehicle, from approximately 0.5% to approximately 10% surfactant, with the remainder of the composition comprising water; and

- (c) combining the two emulsions.

41. A method of producing a sensitized explosive composition including the steps of mixing an emulsified gassing agent with an explosive composition containing a water-in-oil emulsion, the gassing agent comprising a carbonaceous fuel including an emulsifier and constituting a continuous phase and an aqueous phase constituting a discontinuous phase and containing a suitable gas generating material.

42. A method of producing a sensitized explosive composition s defined in claim 41 wherein the gas generating material is sodium nitrite.