US3925123A

US3925123A - Pourable aqueous blasting composition

Info

Publication number: US3925123A
Application number: US514205A
Authority: US
Inventors: Harvey A Jessop
Original assignee: Ireco Chemicals
Current assignee: Ireco Inc
Priority date: 1974-10-11
Filing date: 1974-10-11
Publication date: 1975-12-09
Anticipated expiration: 1992-12-09
Also published as: RO73936A; JPS5852956B2; ZA756087B; PL102607B1; SU615846A3; JPS5163919A

Abstract

A water resistant, stable, pourable, aqueous blasting composition is provided which employes as its thickening system a combination of a non-cross-linked thickening agent and a small amount of a self-complexing thickening agent. The composition is pourable from a package into receptacles as small as three inches in diameter or less.

Description

United States Patent 1 1 1 3,925,123 Jessop Dec. 9, 1975 [5 POURABLE AQUEOUS BLASTING 3,658,607 4/1912 Cook et a1. [49/44 x COMPOSITION Harvey A. Jessop, Murray, Utah IRECO Chemicals, Salt Lake City, Utah Filed: Oct. 11, 1974 App1. No.: 514,205

Inventor:

Assignee:

US. Cl. 149/60; 149/41; 149/42; 149/43; 149/44; 149/60; 149/61; 149/70; 149/76; 149/83; 149/85 Int. Cl. C0613 31/30 Field of Search 149/44, 41, 60, 42, 76. 149/43, 61, 70, 83, 85

References Cited UNITED STATES PATENTS 11/1971 Craig et a1. 149/44 Primary Examiner-Stephen J. Leche rt, Jr. Attorney, Agent, or FirmRobert A. Bingham [57] ABSTRACT A water resistant, stable, pourable, aqueous blasting composition is provided which employes as its thickening system a combination of a non-cross-Iinked thickening agent and a small amount of a selfcomplexing thickening agent. The composition is pourable from a package into receptacles as small as three inches in diameter or less.

4 Claims, No Drawings POURABLE AQUEOUS BLASTING COMPOSITION The present invention relates to an aqueous explosive blasting composition of improved pourability. More particularly, the present invention relates to an aqueous explosive blasting composition having a continuous liquid phase, wherein the phase has a fudge point below intended temperatures of use and comprises an aqueous solution of inorganic oxidizer salt or salts containing a thickening system comprising a combination of a non-cross-linked thickening agent and a small amount of a self-complexing thickening agent. This thickening system renders the composition pourable into receptacles as small as three inches in diameter or less while simultaneously rendering it stable and water resistant. Moreover, this thickening system reduces tackiness and imparts stringiness to the composition such that the composition does not unduly adhere to a package or lose its integrity during pouring.

As used herein, the phrase as small as three inches in diameter or less means the composition must be pourable into a receptacle at least as small as three inches in diameter. According to the present invention, it is possible, however, to prepare effective blasting compositions which are pourable into diameters as small as one-inch or even one-half inch as a practical lower limit.

BACKGROUND Blasting agents of the type commonly known as wa ter-bearing, aqueous or slurry explosive blasting compositions have come into prominent use in recent years. Blasting agents of this type generally comprise a viscous, continuous fluid phase throughout which solid ingredients and gas bubbles may be dispersed, For example, such an agent may comprise an aqueous solution of inorganic oxidizer salts forming the continuous phase of the agent; solid ingredients dispersed throughout the solution such as undissolved oxidizer salts or particulate fuels such as aluminum, carbinaceous materials, sulfur, etc.; organic liquid fuels of either a watermiscible or immiscible nature such as alcohols, glycols, amides and analogous nitrogencontaining liquids generally having good solvent properties for the oxidizer salts and liquid hydrocarbons such as benzene, toluene, fuel oil, etc., respectively; thickening and cross-linking agents and, if desired, numerous, tiny, finely dispersed gas bubbles or microballoons.

Aqueous blasting agents or compositions are usually thickened and thus rendered viscous by the inclusion of hydratable thickeners such as guar gum, starch, flour, etc. Thickening is important for maintaining the homogeneity and integrity and thus stability of a composition. For instance, compositions often contain numerous, finely dispersed gas bubbles which are produced either mechanically by entrainment during formulation or chemically by decomposition of a gassing agent which is included in the composition. Tiny, well-dispersed gas bubbles greatly contribute to a compositions sensitivity to detonation, and proper thickening inhibits bubble migration and coalescence which would reduce this sensitivity. Similarly, thickening inhibits finely divided and dispersed particulate fuel ingredients from gravitationally segregating in the composition. This segregation could reduce the compositions sensitivity and detonating ability. Thus proper thickening is extremely important with regard to composition stability.

A compositions stability can be and frequently is further enhanced by the inclusion of cross-linkers which cross-link the molecules of the thickening agent together thereby forming a chained molecular network which imparts a desired degree of firmness or rigidity to the composition. Thus, in addition to thickening, proper cross-linking can further enhance water resistance and further inhibit constituent migration, segregation and coalescence.

For use in adverse environments such as water-containing boreholes or high-temperature boreholes where degradation of thickening agents may occur, relatively higher amounts of thickening agents are generally employed. In such situations, the thickening agents are usually cross-linked for added stability.

One of the main advantages of aqueous blasting compositions is that they can be used in the presence of water provided they are properly thickened (and preferably cross-linked) so that breakup of the composition and leaching of the soluble oxidizer salts is prevented. These compositions can be formulated and pumped without protective packaging directly into water-containing boreholes. U.S. Pat. No. 3,303,738 discloses a method by which on-site formulation and pumping of a composition into a borehole is accomplished. For use in water containing boreholes, such compositions have obvious advantages over non-slurry, non-water-resistant compositions such as ANFO which require waterproof packaging.

Recently, aqueous blasting agents have been packaged in stick-like form and used as a replacement for stick dynamite. For example, US Pat. No. 3,878,254 describes compositions adaptable for packaging, and U.S.. Pat. No. 3,783,735 discloses an apparatus for preparing and packaging such compositions in stick form. These packaged slurry explosives are generally used in boreholes too small in diameter for filling by direct pumping. Even when packaged, however, these explosives are generally sufficiently thickened for good water resistance in case the package becomes ruptured in a water-containing borehole. Such thickening is also important for the overall stability of the explosive. Normally, these packaged explosives are highly thickened and cross-linked and thus are in the form of a firm gel.

It is oftentimes desirable, and it is the object of the present invention, to have a packaged slurry explosive that can be poured from its package or container into a borehole or receptacle of desired diameter and shape. This packaged blasting agent can be conveniently stored and transported in packages of desired size and then poured into the receptacle or borehole for use. Packaged slurry adaptable for this use will be hereafter referred to as a pourable slurry or pourable blasting agent.

A pourable slurry must be fluid enough for pouring, but at the same time, be sufficiently thickened and cross-linked to be water resistant and stable. Thus the viscosity of the composition must be compromised in order to accomodate both pourability and water resistance and stability requirements. Additionally, since aqueous blasting agents in general tend to be tacky, particularly those which are readily flowable, and thus tend to adhere to the inside of a package when poured, and since many such agents would tend to break apart and lose their integrity during pouring due in part to their adhesion to the package; it is important that the 3 pourable slurry not have undue tackiness and have sufficient stringiness in order that it will maintain its integrity when poured from the package. Stringiness prevents the slurry from tearing apart and also helps the slurry to pull itselfout of the package when it is poured.

Thus the important characteristics of a pourable aqueous blasting agent, vis-a-vis aqueous blasting agents in general, are their thickening and cross-linking characteristics with regard to pourability, water resistancy, tackiness. and stringiness.

It has been found that a thickening system compris ing a combination of a non-cross-linked thickening agent and a small amount of a self-complexing thickening agent is capable of providing a pourable slurry which is water resistant, stable and concomitantly pourable into receptacles three inches in diameter or lessv SUMMARY OF THE INVENTION The present invention comprises a water-resistant, thickened, aqueous, inorganic oxidizer salt-containing, fueled, explosive composition or blasting agent having a continuous liquid phase with a fudge point below intended temperatures of use and containing a thickening system comprising a combination of a non-cross-linked thickening agent and a small amount ofa self-complexing thickening agent, which combination renders the composition pourable into receptacles as small as three inches in diameter or less while simultaneously rendering the composition stable and water resistant.

DESCRIPTION OF PREFERRED EMBODIMENT The compositions of the present invention contain inorganic oxidizer salts dissolved in an aqueous fluid phase. The oxidizer salts are selected from the group which consists of ammonium, alkali and alkaline earth metal nitrates and perchlorates, e.g., sodium, calcium and ammonium nitrates and perchlorates. is essential that substantially all of the oxidizer salt remain in solution at intended temperatures of use of the composition, and, therefore, eutectic combinations of the salts are normally preferred. Thus two or more salts are generally present in the solution, for example, ammonium nitrate (AN) and sodium nitrate (SN) or AN, calcium nitrate (CN) and SN combinations. Although the total amount of salt which can be employed in the compositions and which will remain in solution at intended tmeperatures of use (generally down to at least 5C) can vary substantially depending upon the total amount of water and amount and type miscible organic liquid used, if any, as well as the particular proportions and combinations of oxidizer salts themselves; generally from about 40 to about 70% by weight, based on the total composition, of total oxidizer salts are employed in the compositions of the present invention. The examples given below illustrate several representative amounts and combinations of salts.

Water is an essential ingredient in the compositions since it functions as at least part of the solvent for the oxidizer salts and, by helping to maintain the salts completely in solution, provides sufficient fluidity to a composition to render it pourable. The amount of water required for complete dissolution of the salts in the aqueous solution at intended temperatures of use depends upon that temperature and the various factors listed above and is easily determinable by one skilled in the art. Water is normally present in compositions of the present invention in amounts of from about 10 to about 40% by weight, and preferably greater than 20%.

It is usually desirable, although not essential, that a watermiscible organic liquid fuel be employed both as a fuel and as an additional solvent for the oxidizer salts. Because an organic liquid functions as an extender for water, in addition to its function as a fuel, its inclusion can generally increase the detonation energy of the composition since it can replace part of the water which in high amounts is detrimental to energy production. Typical water-miscible organic liquid fuels are well known in the art and include alcohols, glycols, amides and analogous nitrogen-containing liquids. Several representative liquids are illustrated in the examples below. Such liquids are generally employed in amounts varying from 0 to about 20% by weight.

Although not essential, solid, particulate fuel ingredients common to the art are usually incorporated into the compositions of the present invention. These ingredients are normally added in amounts sufficient or in excess of that required to provide substantially an oxygen-balanced composition. For example, finely divided aluminum particles may be present in amounts of up to 40% by weight or more, although they would usually be present in lower amounts. They should be in finely divided form so as not to unduly interfere with the required fluidity or pourability of the composition.

The thickening system is the important concept of the present invention and comprises a combination ofa non-cross-linked thickening agent and a small amount of a self-complexing thickening agent. This combination renders the composition pourable into receptacles three inches in diameter or less while simultaneously rendering it stable and water resistant.

The non-cross-linked thickening agent provides sufficient thickening to greatly contribute to overall stability and water resistance, but, since it is not cross-linked, the composition remains pourable. An appropriate thickening agent or combination of non-cross-linked thickening agents may also impart high temperature (60) stability to the composition. Typical non-crosslinked thickeners are well known in the art and include flours, starches, polysaccaride polymers such as guar gum, and synthetic polymers such as polyacrylamides or biopolymers. These thickening agents also perform the essential functions of holding in place finely dispersed, sensitizing gas bubbles and preventing substantial segregation of dispersed, particulate ingredients. It is essential that sufficient non-cross-linked thickening agent is present to perform these functions, and it is essential that it not be cross-linked in order that the composition can remain pourable. Although the amount of non-cross-linked thickening agent required depends upon the desired physical characteristics and nature of the composition as determined by its ingredients and the type of thickening agent employed, generally from about 0.2 to about 6% by weight and preferably from about 1 to about 3% is employed.

A self-complexing thickening agent (generally a gum) is an essential ingredient of the invention since it is primarily responsible for imparting stringiness to the composition, and it also reduces tackiness which rende rs the composition more easily pourable from a package. A minimum but limited degree of cross-linking is required for adequate stringiness and generally for good stability, and a self-complexing gum provides such cross-linking in an easily controllable amount. Self-complexing or self-cross-linking" gum contains its own cross-linker which comes into effect when the gum is hydrated in solution. These gums are known in the art and typically include a powdered mixture of guar gum and cross-linker. Antimony, borate and chromate cross-linkers are typically used. A preferred selfcomplcxing gum is Stein-Hall EX-23." Other gums from the series can be used. General Mills also manufactures many self-complexing gums. The self complexing thickening agent is generally present in an amount of from about 0.l to about 0.5% by weight and preferably from about 0.l to about 0.3%.

The inclusion of a self-complexing thickening agent reduces the total amount of thickeners required since it provides a limited but a necessary threshold amount of cross-linking. lt is extremely difficult by conventional means to control reliably the degree of cross-linking of an aqueous blasting agent where that degree must necessarily be maintained at a very small amount in order for the composition to be pourable. Thus it is difficult if not practicably impossible to add cross-linker to a thickened solution as a separate ingredient and attempt to limit the degree of cross-linking to a very small amount in order for a composition to remain pourable. However, if most of the thickening agent is non-crosslinked. and the small amount of cross-linking that is required can be provided by selectively cross-linking only a small portion of total thickening agent, reliable control becomes feasible. This control is accomplished by the use of a self-complexing gum which is selectively cross-linked by its own self-contained cross-linker. Thus cross-linker need not be separately added to a composition, and an accurate means of reliably controlling the degree of cross-linking of the composition is accomplished by varying as desired the amount of self-complexing thickening agent added.

The invention can be better understood by reference to the examples given below.

EXAMPLE 1 A composition of the present invention (and compositions of the present invention in general) was (can be) prepared in the following manner: the oxidizer salts were dissolved in water to form a solution having a fudge point of approximately 0C. The solution was heated to about C or C and then the watermiscible liquid fuel and guar gum were added. The resulting solution mixture was allowed to thicken and was then mixed to homogeneity with the remaining ingredients including the self-complexing gum and starch thickeners. Mixing and pumping was accomplished by conventional means. This blasting agent had the following composition (percentages are by weight):

Sclf-complcxing (lum (EX-23] The solution of this composition had a fudge point of 2C. At 30C. the solution had a viscosity of 800 to l200 centipoiscs. It has a pH of 4.0 i 0.2 and a density of 1.33 g/cm at 30C. At 5C. the composition had a critical diameter (the minimum charge diameter for successful propagation of a detonation wave) of from 2 to 2 A inches at a density of 1.2] g/cm.

The composition of this example is water resistant and is pourable from a polyethylene package having a diameter of five inches into a three inch diameter borehole or other receptacle.

The thickening system of this example, comprising non-crosslinked guar gum, non-cross-linked starch, and self-complexing gum, is particularly effective. This combination provides concomitantly high temperature (up to 60C) stability and low temperature (down to 5C) pourability. The starch provides thickening which is stable at high temperatures; the non-cross-linked gum provides good overall thickening of the liquid phase without adversely affecting pourability; and the self-complexing gum reduces tackiness and imparts stringiness which enhances integrity during pouring and addes to overall water resistance.

EXAMPLE 2 Other compositions were prepared in the manner described above and have the fonnulations, properties and etonation results indicated in Table 1 below. All of these compositions are water resistant and capable of being effectively poured from a container such as a polyethylene bag into a receptacle as small as three inches in diameter or less. The compositions are not unduly tacky and have good stringiness and thus maintain their integrity during pouring.

The compositions of the present invention can be packaged by conventional means in a container or package of essentially any desired size and shape. They are preferably packaged in an elongated or cylindrical polyethylene bag having an average cross-sectional diameter of about five to about seven inches. The packaged composition generally has a safe, reliable storage life of up to about one year or more under reasonable storage conditions. When the packaged explosive is to be used, the package is opened or cut, usually at one end, and the composition poured" out of the package and into a desired receptacle. Even though the composition is pourable from a package, it is nevertheless sufficiently thickened and has at least a minimum degree of cross-linking (having a viscosity of generally about 15,000 to about 75,000 centipoises) to be water resistant and stable and thus can be poured into water-containing receptacles or boreholes and can be detonated even after remaining in a water-containing borehole for many days. At l5,000 centipoise, compositions of the type shown in the above examples are pourable into two inch diameter receptacles. At 75,000 centipoises, the compositions are still pourable into 2% to 3 diameter receptacles.

While the present invention has been described with reference to certain illustrative examples and preferred embodiments, various modifications will be apparent to those skilled in the art and any such modifications are intended to be within the scope of the invention as set forth in the appended claims.

TABLE I Composition C Ingredients (parts by weight) AN 38 22 25 I lip s ercilia What is claimed is:

1. In a water resistant explosive composition which contains an aqueous inorganic oxidizer salt solution forming a continuous fluid phase throughout the eomposition and having a fudge point below intended temperatures of use of the composition; the improvement comprising a thickening system consisting essentially of a combination of non-cross-linked guar gum and starch and a small amount of a self-complexing thickening agent, which thickening system simultaneously provides water resistance, stability at temperatures as high as 60 C and pourability into receptacles as small as 3 inches in diameter or less at temperatures as low as 5 C 2. A composition as defined by claim 1 wherein water is present in an amount of about 10 to about 40% by weight.

3. A composition as defined by claim 1 comprising about .2 to 3% by weight guar gum, about 0.5 to 2% starch and about 0.05 to about 0.25% of the self-complexing gum.

4. A composition as defined by claim 3 comprising about 40 to by weight of an inorganic oxidizer salt selected from the group consisting of ammonium, alkali and alkaline earth metal nitrates and perchlorates and mixtures thereof; about 10 to 40% water; from about 0 to about 20% of a water-miscible organic liquid fuel and from 0 to about 40% of particulate fuel.

Claims

1. IN A WATER RESISTANT EXPLOSIVE COMPOSITION WHICH CONTAINS AN AQUEOUS INORGANIC OXIDIZER SALT SOLUTION FORMING A CONTINUOUS FLUID PHASE THROUGHOUT THE COMPOSITION AND HAVING A FUDGE POINT BELOW INTENDED TEMPERATURES OF USE OF THE COMPOSITION; THE IMPROVEMENT COMPRISING A THICKENING SYSTEM CONSISTING ESSENTIALLY OF A COMBINATION OF NON-CROSS-LINKED GUAR GUM AND STARCH AND A SMALL AMOUNT OF A SELF-COMPLEXING THICKENING ASENT, WHICH THICKENING SYSTEM SIMULTANEOUSLY PROVIDES WATER RESISTANCE, STABILITY AT TEMPERATURES AS HIGH AS 60*C AND POURABILITY INTO RECEPTACLES AS SMALL AS 3 INCHES IN DIAMETER OR LESS AT TEMPERATURES AS LOW AS 5*C.

2. A composition as defined by claim 1 wherein water is present in an amount of about 10 to about 40% by weight.

4. A composition as defined by claim 3 comprising about 40 to 70% by weight of an inorgaNic oxidizer salt selected from the group consisting of ammonium, alkali and alkaline earth metal nitrates and perchlorates and mixtures thereof; about 10 to 40% water; from about 0 to about 20% of a water-miscible organic liquid fuel and from 0 to about 40% of particulate fuel.