NO841906L - STABLE EXPOSURE ON AMMONIUM NITRATE / EMULSION BASIS AND EMULSION FOR USE THEREOF - Google Patents

Description

This invention relates to explosives comprising a sensitized mixture of a water-in-oil emulsion and solid, particulate ammonium nitrate (AN), e.g. AN beads or granules which may be coated with fuel oil (ANFO), especially such explosives in the form of storage-stable packaged products and products in loose weight adapted to be pumped down boreholes. The invention also relates to a low-viscosity emulsion which is particularly suitable for mixing with fuel-free or fuel-poor AN to form such a mixture.

Explosives comprising a mixture of a water-in-oil emulsion and solid, particulate AN (e.g. ANFO) have attracted the interest of explosives manufacturers in recent years because they offer the advantages of emulsion explosives in terms of high bulk density , high explosive power and good water resistance, while at the same time they entail reduced costs as a result of the lower costs for AN. Among the problems that can be encountered in connection with the use of these mixtures, however, are problems with the pumpability of the mixture and problems with the stability of the mixture, especially with the stability of the explosive properties of the mixtures. Some mixtures are not pumpable or pumpable only with difficulty. Some must be pumped immediately after they are formed, because they do not retain their pumpability even for a day or two. Although it is quite clear that the mixture must have a sufficiently good storage stability for it to be detonable after being placed in a borehole, this topic has not been given much attention in the previous publications dealing with emulsion/AN mixtures . Equally, it is a fact that not all packaged mixtures are detonable at the time when they are to be used, even if the packages have only been stored for a short time.

Emulsion/AN mixtures are described in US Patent Nos. 3,161,551, 4,111,727, 4,181,546 and 4,357,184 and in British Patent No. 1,306,546. In US Patent No. 3,161,551 an emulsion/AN is described -mixture where the emulsion, which is stated to be in a sensitized form, is used as a sensitizing agent for the solid ammonium nitrate. With regard to the placement of the mixture in a borehole, the patent holder mentions formation of the mixture in the borehole itself, namely by dropping the AN component into the hole and pouring the sensitized emulsion over it.

In US Patent No. 4,111,727, where emulsion/AN mixtures in the ratio 10/90-40/60 are sensitized only with the air contained in the AN component, it is stated that the emulsion and the AN particles are combined by means of very simple procedures, preferably just before placement in the borehole. In this patent, it is also stated that sorbitan monooleate, sorbitan monostearate and sorbitan monopalmitate are suitable as emulsifiers for producing the emulsion, and that the emulsifiers are preferably mixed into the oil before the aqueous component is added. The AN used according to the US patent can be oxygen-balanced ANFO (for mixing with an oxygen-balanced emulsion) or fuel-poor or fuel-free solid AN (for mixing with an emulsion containing most or all of the oil required for to give the mixture oxygen balance)..

US Patent No. 4 181 546 describes emulsion/AN mixtures in the ratio of 40/60-60/40 where the spaces in and between the AN particles are completely filled. This product is stated to contain too large a proportion of dry constituents for it to be pumpable with conventional mud pumps, but it is stated to be able to be delivered to a borehole using a screw conveyor in the same way as dry ANFO. According to this patent document, it is recommended to use as small an amount of emulsifier as possible and to carry out mixing using high shear forces in order to obtain a stable emulsion. In the patent, sorbitan fatty acid esters are stated to be particularly suitable emulsifiers, and "Glycomul O" (sorbitan monooleate) is stated to be better than most as far as the invention described there is concerned.

In British Patent No. 3,306,546, the mixture described there is filled into a polyethylene tube with a diameter of 8.3 cm, after which nitroglycerin is added to the charge as an initiating explosive and the charge is detonated 1 hour after the mixing operation. Neither in US patent documents no. 3 161 551, 4 111 727 and 4 181 546 nor in British patent document no. 1 306 546 do you deal with such questions as the stability of the mixture, i.e. the condition of the mixture after it has stood for several days or weeks before or after packaging or before it is delivered in bulk to a borehole.

The emulsion portion of the explosive according to US Patent No. 4,457,184 is termed a "microemulsion", and it contains an amphiphatic synthetic polymer as an emulsifier, together with a conventional water-in-oil emulsifier. Optionally, a stabilizer consisting of a phosphatide emulsion is also incorporated. The microemulsion according to this US patent, which is described as a "liquid-liquid-foam" with very small cell size varying from less than 1 µm to approx.

15 µm, is indicated in itself to exhibit exceptionally good storage stability and to withstand the addition of additional amounts of fuel and energy-enriching components. The patent holders explain a destabilizing seed crystal effect in the previously known emulsion explosives, which is due to the presence of solid oxidizer salts in the base emulsion. According to the aforementioned US patent document no. 4 357 184, it has been shown that the microemulsion described there, when 24% ground AN was added, was far more stable against this seed crystal effect than a previously known emulsion and remained cap sensitive through three

o cycles, each consisting of three days of storage at 5 0 C followed by 2 - 3 days at -17°C.

The assessment of storage stability carried out in

The US patent is mostly aimed at the explosive emulsion itself. The patent holders mention that all previously known water-in-oil emulsions show insufficient stability as a result of the nucleation effect. The patent holders also suggest that the nucleation effect is a problem in connection with AN-added emulsions, although they do not explain how this can be the case in microemulsions containing relatively large AN particles. However, according to this US patent, an expensive polymeric emulsifier and possibly an emulsion stabilizer are required to achieve improved stability of the microemulsion.

AN/emulsion mixtures with good storage stability and

a method for producing such mixtures which does not require the use of expensive additives of perhaps limited applicability is badly needed to expand the range of AN/emulsion mixtures which can be made available to the general public.

In particular, there is a need for mixtures that can be pumped in

in a borehole even a few days after they have been formed,

and which are detonable after they have been placed in a borehole in packaged form approx. 3 months or more from the time of preparation of the mixtures.

With the present invention, an improved method for producing an explosive is provided in that particles of ammonium nitrate (AN), e.g. AN or ANFO beads, are combined with a water-in-oil emulsion comprising (a) a liquid carbonaceous fuel containing components that form a continuous emulsion phase, (b) an aqueous solution of an inorganic oxidizing salt that forms a discontinuous emulsion phase dispersed as separate small droplets in the continuous phase, and (c) an emulsifier which forms a mixture of the AN particles and the emulsion containing a sensitizing amount of dispersed gas bubbles or voids. The distinctive feature of the invention is that the AN particles and emulsion components are formed into a structure that minimizes water loss from the small drops of the aqueous solution and transfer of the water through the continuous phase to the AN particles that are mixed with the emulsion. Preferably, this structure includes an emulsion which, when subjected to the water diffusion test described below, does not lose more than approx. 4%

of its original weight:

A cylindrical pan of radius 7.5 mm and height 2.6 mm is filled with 0.325 ml of freshly prepared emulsion, which is the same emulsion used in the preparation of the mixture. The flat, exposed surface of the emulsion of 1.25 cm 2 is brought into contact with a cylindrical pellet of ammonium nitrate having the same cross-sectional area as the emulsion sample and a height of

at least 1 cm. The ammonium nitrate is the same as that which had been used in the preparation of the mixture. The sample of emulsion/AN is stored for 48 hours in dry air at 25°C, after which the emulsion is analyzed for water loss.

According to a preferred method according to the invention, the described structure that prevents water loss and water transfer is formed by the AN particles being combined with an emulsion which in the emulsifier system contains (a) a salt, preferably an alkali metal, ammonium and/or alkylammonium salt of a fatty acid (preferably selected from saturated mono-, di- and tri-unsaturated monocarboxylic acids containing from 12 to 22 carbon atoms) in addition to (b) the free fatty acid, the latter present in solution in an oil, the oil solution constituting the continuous emulsion phase and the fatty acid and the fatty acid salt, together with said oil make up said liquid carbonaceous fuel. Most preferably, the fatty acid salt emulsification system is a system formed in situ from a fatty acid and a base after the oil and the aqueous solution of the inorganic oxidizing salt have been brought together to form the emulsion. With this emulsification system, a base is present, e.g. hydroxide, in the aqueous phase of the emulsion.

An alternative, or preferably supplementary, method of forming the structure that prevents water transfer between the small droplets of the aqueous solution and the AN particles is to form a droplet cell size of at least approx. 1 pm and preferably at no more than approx. 4 um. Alternatively, or as a supplement, the structure can be formed by coating the AN particles with a substance that in water has a diffusion coefficient

o -5 2

at 25 C in less than approx. 10 cm/second.

The invention also provides a storage-stable, packaged product which is produced using an embodiment of the method according to the invention, and which comprises a stored mixture of preferably at least 30% by weight AN particles, e.g. ANFO beads, and preferably at least 30% by weight of an emulsion comprising (a) a liquid, carbonaceous fuel including an oil solution of a fatty acid, which solution forms a continuous emulsion phase, (b) an aqueous solution of an inorganic oxidizing agent

salt forming a discontinuous emulsion phase dispersed as separate small droplets in the continuous phase, and (c) an emulsifier system including an emulsifier comprising a salt, preferably an alkali metal, ammonium or alkylammonium salt of a fatty acid (preferably selected from mono-, di- and tri-unsaturated monocarboxylic acids containing from 12 to 22 carbon atoms) in addition to the free fatty acid, the fatty acid and the fatty acid salt together with the aforementioned oil forming the liquid, carbonaceous fuel, which mixture

contains a sensitizing amount of dispersed gas bubbles or voids, e.g. an amount corresponding to at least approx. 5% of the volume of the mixture, and whose structure is such that the amount of water lost from the small drops of the aqueous solution in the emulsion after aging at 25°C for two days is not greater than approx. 4, and preferably not larger than approx. 3.5% of the original weight of the emulsion, measured by the water diffusion test described above. In a preferred embodiment, the emulsion has a droplet cell size of at least approx. 1 (am, and which is preferably no larger than approx. 4 um.

The term "aged" is used here to distinguish the packaged product according to the invention from products that are produced at the point of use, and which are placed in a borehole in loose weight. An "aged" product here refers to a product that is packaged and transported to the place of use at a later date.

point, usually several days, and often several weeks, after the manufacture.

With the term "ammonium nitrate particles" used here to describe the solid material present in the product according to the invention in mixture with an emulsion,

means ammonium nitrate in the form of granules or beads, e.g. fuel-free or fuel-poor beads, or beads that are lightly coated with fuel oil, e.g. the well-known "ANFO", where the weight ratio AN/FO is usually approx. 94/6, and/or is coated according to the method according to the invention, as will be described below.

According to a further aspect of the invention, there is provided a water-in-oil emulsion which is adapted to be mixed with AN beads according to an embodiment of the method according to the invention for forming a stable explosive, which emulsion comprises (a) from 7 to 21% by weight, preferably from 9 to 15% by weight, of a liquid, carbonaceous fuel including an oil solution of a fatty acid, which solution forms a continuous emulsion phase,

(b) an aqueous solution of an inorganic oxidizing agent

salt forming a discontinuous emulsion phase dispersed as separate small droplets in the continuous phase, and

(c) an emulsifier system comprising (1) the aforementioned

fatty acid and (2) a fatty acid salt, the oil, fatty acid and fatty acid salt together forming the liquid carbonaceous fuel, and the ratio of the amounts of oil and fatty acid supplied to form the emulsion being in the range of 1/1

to 3/1 on a weight basis; which emulsion has an oxygen balance that is more negative than approx. -6%, e.g. as negative as approx. -50%.

In a preferred emulsion, where the emulsifier system is one formed in situ from the fatty acid and a base after the oil and the aqueous salt solution have been brought together to form the emulsion, a base is also present as a result of the addition of the base and fatty acid in an equivalent ratio of from 0.5/1 to 3:1, preferably from 1.5/1 to 2/1. In the quantity ratio between oil and fatty acid in this given emulsion stated above, the amount by weight of fatty acid is to be understood as the amount by weight of fatty acid that has been added to form the emulsion. Part of this is transferred to the fatty acid salt emulsifier. This emulsion has a viscosity which is usually in the range of 500 to 10,000 poise, and which is usually from 500 to 3,000 poise for bulk products. The structure of the emulsion is stable for approx. 3 months or more.

In the emulsion product produced by addition

of a pre-formed fatty acid salt to the system, the weight amount of "fatty acid" in the above stated ratio between oil and fatty acid shall be understood as the weight amount of the added fatty acid plus the weight amount of fatty acid salt added after the emulsion has been formed. In this product, the ratio between the weight amount of fatty acid salt (added) and the weight amount of fatty acid (added) is at least approx. 0.5/1.

The amount of inorganic oxidizing salt (the oxidizing agent) present in the emulsion according to the invention is insufficient for complete combustion of the fuel therein, as is evident from the emulsion's negative oxygen balance. This emulsion, which does not contain a sufficient amount of oxidizing agent, is transferred to a product with a more positive oxygen balance and with satisfactory explosive properties by mixing it with fuel-poor or, preferably, essentially fuel-free AN beads. Due to its relatively low viscosity, the oxidizer-poor emulsion can be mixed with these AN beads using low shear forces to form a preferred explosive emulsion/AN mixture according to the invention containing from 20 to 70% by weight of AN beads and a sensitizing amount of dispersed gas bubbles or voids (e.g. an amount corresponding to at least 5% of the volume of the mixture), as the mixture is essentially oxygen-balanced, i.e. exhibits an oxygen balance that is more positive than approx. -25% and is preferably in the range from -10 to +5%. Mixtures prepared from the preferred in situ emulsion

and from 20 to 50% pearls have a viscosity in the range from 2500 to 20,000 poise, and a viscosity in this range can be maintained for several days.

In the attached drawing, which shows diagrams drawn up on the basis of data obtained in the experiments described in examples 1, 2 and 7, fig. 1 a diagram showing the rate at which water is transferred into an emulsion used in a product according to the invention, compared to an emulsion used in a previously known product, fig. 2 is a diagram showing the rate at which water is transported into solid ammonium nitrate from an emulsion used in a product according to the invention, compared to an emulsion used in a previously known product, and fig. 3 is a diagram showing the viscosity of three mixtures according to the invention and three control mixtures as a function of time.

The present invention is based on the recognition that the transfer of water from the dispersed aqueous phase of the emulsion to the AN particles mixed with the emulsion in the AN/emulsion mixtures plays a major role in the instability of these mixtures, leading to a deterioration of the product properties. This transfer of water results in an increase in the water content of the particulate AN, perhaps to an amount of from 5 to 10%, and an increase in the salt concentration in the dispersed aqueous phase, which approaches the saturation limit and the possibility that salt can crystallize out. These combined effects can cause the structure of the emulsion/AN mixture to deteriorate rapidly.

In the method according to the invention, the AN particles and the components of the emulsion, as a result of their chemical composition and physical properties (e.g. size and spatial conditions), are formed into a structure in the emulsion/AN mixture that minimizes the loss of water from the small droplets of aqueous salt solution and the transport of the water through the continuous phase of the emulsion to the AN particles. This structure provides a medium or a barrier which inhibits water transport, and which is preferably formed by a mainly hydrophobic continuous emulsion phase, which is preferably obtained when the emulsifying system contains a salt, preferably an alkali metal, ammonium and/or alkylammonium salt of a fatty acid (e.g. . a saturated or mono-, di- or tri-unsaturated monocarboxylic acid containing from 12 to 22 carbon atoms), besides the free fatty acid in solution in an oil, the oil solution of the acid forming the continuous phase of the emulsion and the oil, the fatty acid and the fatty acid salt together forming the liquid carbonaceous fuel. Most preferably, this emulsifier system is formed in situ by bringing the oil and the aqueous solution together in the presence of a fatty acid and a base, according to the method described in US patent document no. 4,287,010. It has been suggested that the method according to said US patent document can allow the emulsifier consisting of a fatty acid salt (soap) to form at the interface between oil and water, where it is present together with free fatty acid, whereby it is assumed that a stabilizing equilibrium is established between the acid and the soap at the interface between fatty acid in the oil phase and base in the aqueous phase .

According to the most preferred embodiment of the method according to the invention, the emulsifier system is therefore one which has been formed by in situ formation of a salt, preferably an alkali metal, ammonium or alkylammonium salt of a fatty acid (preferably a saturated or mono-, di- or tri-unsaturated monocarboxylic acid containing from 12 to 22 carbon atoms), most preferably sodium, potassium and/or ammonium oleate, according to methods described in the above-mentioned US Patent No. 4,287,010.

The importance (for the stability of emulsion/AN mixtures) of a mixture structure provided by means of an emulsion containing a hydrophobic, continuous emulsion phase, and more particularly a relatively non-polar emulsifier system which provides such a continuous phase, has not been recognized so far. IN

US Patent No. 4,181,546 states the sorbitanoleate type (nonionic) to be among the most useful emulsifiers. IN

US Patent No. 4,357,184 suggests that the stability is dependent on the presence of an emulsifier which is a graft polymer, a block polymer or a branched polymer,

in combination with conventional emulsifiers. High concentrations of the polar, non-ionic emulsifiers in the oil layer make this relatively hydrophilic and therefore able to transport water to the AN particles at high speed, which leads to the product instability described above. The advantage obtained with the hydrophobic oil layer, compared to the more hydrophilic oil layer preferred according to US Patent No. 4,181,546, is shown in Examples 1 and 2 below.

The regulation of the emulsifier system described above is the preferred method of providing a structure where a hydrophobic medium is present between the aqueous droplets in the emulsion and the AN particles. An alternative method, which is applicable to any emulsifier system but which is preferred together with the preferred emulsifier system described above, is to coat the AN particles with a substance of low water diffusivity, e.g. a substance in which water has a diffusion coefficient

o -5

at 25 C which is less than approx. 10 and preferably less than

— 8 2

about. 10 cm/sec. Preferred coating materials are those which, when used in an amount which constitutes 6 - 10% of the amount of solid AN used, can serve as a fuel to give the solid AN oxygen balance. Such materials would e.g. could be-

replace the fuel oil (FO) that is normally used in ANFO. Examples of such materials are solid or semi-solid hydrocarbons, including paraffin wax and petrolatum-rosin-paraffin.

In a further preferred embodiment of the invention, the desired structure formed by the AN particles and the components of the emulsion is provided by the cell size of the emulsion's internal phase (the small droplets of the aqueous salt solution) being regulated so that a reduction of the chemical driving force is achieved, i.e. of the difference between the chemical potential of the water in the emulsion's dispersed aqueous salt solution and the AN particles. A reduced chemical driving force reduces the rate at which water is transported from the aqueous emulsion phase to the AN particles. The chemical potential for the components in the dispersed aqueous phase increases inversely proportional to the radius of the cell's (droplet's) circumference. Therefore, a smaller cell size will increase the water's chemical potential in the discontinuous phase, whereby the driving force for water transport to the solid oxidizing agent is increased. Previously, a smaller cell size (higher viscosity) was recommended to in itself increase the stability of emulsion explosives. Thus, in US patent document no. 4,181,546 it is recommended to use large shear forces during the mixture and to use a "good emulsifier" (of the sorbitanoleate type) in order to obtain a good and stable emulsion. As discussed above, the situation is different for emulsion/AN mixtures. The optimal cell size in the internal phase of an emulsion in a mixture is the largest cell size that will not lead to crystallization as a result of water loss during the storage time calculated for the product. This ensures minimal water transport, without premature crystallization of the emulsion. The optimum cell size is usually from 1 to 4 µm and decreases with decreasing content of water in the aqueous phase.

Other factors can also be regulated to minimize the transfer of water through the continuous phase of the emulsion. As the water transfer is not only determined by the composition of the continuous phase, but also decreases with increasing dimensional thickness of this phase, the continuous phase can be made dimensionally thicker by increasing the emulsion's oil content. Therefore, a preferred product according to the invention, especially for use in emulsion/AN mixtures for use in bulk, is an emulsion with a high oil content containing a part of, and preferably substantially all, the oil required to provide oxygen balance to the solid ammonium nitrate to be mixed with the emulsion. This is beneficial for several reasons. Firstly, the added oil gives the emulsion a lower viscosity. Low viscosity is a major advantage in that it enables the formation of emulsion/AN mixtures which can be mixed using lower shear forces, which has a beneficial effect on the stability of the mixture. Mixing using low shear forces is particularly important when producing mixtures with a high content of solid AN or ANFO, because the movement of the particles past each other during mixing involves a processing of the emulsion between them which can break the oil film that separates the particles from the small droplets of the aqueous solution and thereby give the water transport a "flying start". With the emulsion with a high oil content according to the invention, and especially with the preferred emulsion in which the emulsifier system is formed in situ, a more stable mixture is obtained, because the components can be mixed using lower shear forces than those used when mixing a more viscous emulsion, and the a less viscous, easier to pump mixture is obtained. Moreover, as will be further explained later, the lower viscosity of the mixture is sufficiently stable, at least for several days, so that the advantage of the good pumpability is maintained even if a few days pass between the time when the mixture is prepared and the time then. it is pumped.

As stated above, increasing the oil content of the emulsion to increase the dimensional thickness of the emulsion's continuous phase will increase the resistance to transport of water through the continuous phase to the AN particles. However, uncontrolled expansion of the continuous phase of the emulsion will often cause separation of the oil or "creaming".

It has now been shown that in certain specific systems an emulsion which has a high oil content, and which has an emulsion structure which is stable, i.e. a structure where the oil phase does not give rise to any "cream formation", can be obtained if the concentration of the emulsifier is higher than that used in standard emulsions with a low oil content, i.e. in mainly oxygen-balanced emulsions to be mixed with ANFO. If the emulsifier is a salt of a fatty acid used in combination with the free fatty acid, which is present in solution in the oil, and especially if the salt of a fatty acid has been formed in situ as described in US Patent No. 4,287,010, the stable, low-viscosity emulsion (ie the high-oil emulsion containing more emulsifier in the same ratio) form mixtures with AN with a stable viscosity that remains sufficiently low to enable pumping, even if the mixture is "aged" a day or so before pumping.

Nonionic emulsifiers, such as those of the sorbitan fatty acid ester type, are indicated in the art, namely in US Patent No. 4,181,546, to have been found to be among the most useful emulsifiers for emulsions in terms of stability. However, it is a recent realization that emulsion/AN mixtures prepared from high oil emulsions, containing an emulsifier at a concentration sufficiently high to maintain the emulsion structure, are unstable with respect to the viscosity level when the emulsifier is sorbitan monooleate. In the latter case, despite the lower viscosity of the high-oil emulsion used to prepare the mixture, water transport from the mixture, water transport from the aqueous phase and the possible crystallization of the salt therein can cause an extremely rapid increase in the viscosity of the mixture to a level at which the mixture is no longer pumpable and subsequently no longer detonable. This level can be reached within a day or two. Accordingly, viscosity stability is not a characteristic property of high oil emulsion/AN mixtures in general, but is dependent on the nature of the emulsifier system present in the high oil emulsion.

Other advantages of forming mixtures of the emulsion with a high oil content according to the invention and oil-free or oil-poor AN beads are that the void volume in the AN beads could be useful as sensitizing sites in the mixture. Moreover, incorporating all the necessary oil into the emulsion from the beginning makes it possible to keep the quantity ratio between oil and fatty acid essentially undisturbed during the conversion from the unmixed to the mixed emulsion, so that the necessary content of emulsifier is maintained.

Assuming that the preferred emulsion with a high oil content according to the invention is to be mixed with 20 - 70% AN beads, the amount of liquid carbonaceous fuel (oil plus fatty acid plus fatty acid salt) present in this emulsion will usually be in the range of 7 to 21 %, calculated on the total weight of the emulsion. The amount of liquid carbonaceous fuel in this emulsion is the greater the greater the content of AN beads in the mixture in which the fuel is to be used.

In the preferred mixing ratio between emulsion and AN-

beads of from 40/60 to 60/40, the emulsion's content of liquid fuel varies in the range from 9 to 15% by weight, the content being no higher than approx. 13% in emulsions to be used in products delivered in bulk, in which it is advantageous not to use more than approx. 50% pearls for reasons of pumping.

The amounts of inorganic oxidizing salt(s) and water

present in the aqueous phase of the high oil emulsion are within the broad ranges indicated for these components in US Patent No. 4,287,010, namely from 5>0 to 95% by weight oxidizing salt(s) and from 5 to 25% by weight

water. Within these areas, however, higher water concentrations are preferred, namely from 12 to 20%. The content of inorganic oxidizing salt(s), liquid carbonaceous fuel and water in emulsions with a low oil content used in the present process, and in the packaged pro-

duct according to the invention, will be as described in US Patent No. 4,287,010.

In the preparation of the emulsifier system according to

the in situ method which is described in the above-mentioned US patent document no. 4 287 010, a fatty acid, e.g. oleic acid, and a base together at the same time as an aqueous solution of an inorganic oxidizing salt and an oil, whereby a fatty acid salt emulsifier is formed in situ as a water-in-oil emulsion is formed. The fatty acid salt is present in the resulting emulsion, together with the fatty acid (in the oil phase). Base is also present, namely in the aqueous phase.

The fatty acid salt emulsifier used in the preferred embodiment of the present method can be a salt of a saturated or mono-, di- or tri-unsaturated monocarboxylic acid containing at least 12 and usually no more than 22 carbon atoms. Examples of such acids are oleic acid, linoleic acid, linolenic acid, stearic acid, isostearic acid, palmitic acid, myristic acid, lauric acid and brassidic acid. The free fatty acid present may be selected from this same group of monocarboxylic acids. Oleic acid and stearic acid are preferred because they are easy to obtain. In emulsions with a high oil content for delivery in bulk, a fatty acid should be chosen, e.g. oleic acid, which is liquid at the temperature at which the mixture is expected to be used. Usually this will be an unsaturated monocarboxylic acid. The cation part of the fatty acid salt is preferably an alkali metal ion (e.g. a sodium, potassium or lithium ion), an ammonium ion or a mono-, di- or trialkylammonium ion where the alkyl group(s) preferably contain 1-3 carbon atoms. Sodium, potassium and ammonium oleates are preferred.

As will be seen from the following example 6, the emulsion structure of the emulsion with a high oil content according to the invention is many times more stable than a comparable emulsion with a lower emulsifier concentration. To provide the higher concentration of emulsifier in the high oil emulsion, the weight ratio of oil to fatty acid added to form the emulsion must be in the range of 1/1 to 3/1. If pre-prepared fatty acid salt is used (d<y>is added) to form the emulsion, the weight amount of "fatty acid" in this quantity ratio shall be understood as the weight amount of added fatty acid plus the weight amount of added fatty acid salt, and the weight ratio between fatty acid salt (added)

and fatty acid (added) must be at least 0.5/1. The base/acid equivalent ratio used in the production of the emulsion with a high oil content by the in situ method must be in the range from 0.5/1 to 3/1, preferably from 1.5/1 to 2/1.

In the practice of the present invention, oils and aqueous solutions of inorganic oxidizing salts which are known to be used in the field of explosive emulsions can be used. Preferably, those described in the above-mentioned US patent no. 4,287,010 are used. Most often, the inorganic oxidizing salt that is present in the aqueous phase of the emulsion will be an ammonium, alkali metal or alkaline earth metal nitrate or perchlorate, preferably ammonium nitrate, either alone or in combination with e.g. up to 50% sodium nitrate (calculated on the total weight of inorganic oxidizing salts in the aqueous phase). Salts with monovalent cations are preferred, as indicated in US Patent No. 4,287,010. Suitable oils for use in the liquid carbonaceous fuel include fuel oils and lubricating oils of the heavy aromatic, naphthenic or paraffinic type, mineral oil, dewaxed oil,

oil.

The emulsion with a high oil content according to the invention is prepared by stirring the aqueous solution of oxidizing salt and the oil solution of the fatty acid in the presence of the fatty acid salt, under such conditions that a stable emulsion with a selected viscosity is obtained. In the preferred in situ system, the base is preferably dissolved in the aqueous solution, which is then stirred with the oil solution of the fatty acid.

This emulsion can be mixed with AN beads (or AN granules) by pumping it into a mixer or into a screw conveyor that transports the AN beads. The latter method is appropriate for the production of a packaged product. As a result of the rotation of the screw in the screw conveyor, the emulsion and beads are mixed, while the mixture is conveyed to the place where the packaging takes place. The low viscosity of the emulsion allows the mixing operation to be performed in a shorter screw conveyor using lower shear forces, resulting in an improved storage stability compared to mixtures prepared using high shear forces.

If the mixture of emulsion with a high oil content and AN beads is to be used in loose weight, e.g. by being pumped from

a mixer and down a borehole, perhaps after it has been in the mixer for a day or so, the mixture remains pumpable after such a period as a result of its viscosity stability,

as shown in Example 7. The viscosity of freshly prepared mixture of an emulsion prepared by the in situ method and containing from 20 to 50% AN beads is usually in the range from 2500 to 20,000 poise, and the mixture maintains for several days a viscosity within this range which is sufficient to enable pumping during this period.

The AN beads with which the high-oil emulsion is mixed are a low-oil product, preferably mainly oil-free AN beads. To produce a mixture that is pumpable, a sufficiently large quantity of beads is used to form a mixture with a bead content of from 20 to 50% by weight. Up to 70% by weight of pearls can be used in a packaged product.

The emulsion/bead mixture according to the invention is available, whether it is made with AN beads or ANFO beads, in a sensitized form, so that it can be detonated by means of devices which are commonly used to initiate explosives. For this purpose, the mixture contains a sensitizing amount (e.g. at least 5% by volume) of dispersed gas bubbles or voids (calculated on the volume of the mixture). This cavity or gas volume can be that which the AN beads themselves contain (see example 5), or gas can be incorporated by adding other air-bearing solid materials, e.g. phenol-formaldehyde microballoons, glass microballoons, fly ash, etc. If materials of the latter type are to be present in the mixture, they may form a component of the emulsion, or they may be added at the time of the mixing operation. For mixtures containing less than approx. 50% AN beads, an additional supply of gas bubbles or cavities usually has to be made until the emulsion begins to sensitize it.

As mentioned above, the fatty acid salt-emulsifier system is the preferred means for producing the structure which minimizes water loss and water transport in the method according to the invention. This agent is used with the greatest advantage when the fatty acid salt emulsifier system is used in combination with a high oil content, regulation of the cell size and/or AN coating, etc. In the present method, however, the latter techniques can also be used together with other emulsifier systems.

The present method is advantageously used for the production of mixtures containing from 20 to 70% by weight of AN particles. The need for a barrier against water transport and/or a reduced chemical driving force is usually not that great for mixtures containing less than 20% AN. The AN content will typically range from 30 to 70% by weight for a packaged mixture and from 20 to 50% by weight for a pumped mixture.

Explosives which are mixtures of a water-in-oil emulsion and AN or ANFO beads with a physical and chemical structure that minimizes water loss and water transport from the aqueous phase of the emulsion according to the method according to the invention, and in particular mixtures of the emulsion with a high oil content according to the invention and AN beads, are applicable both in loose weight and in packaged ferm. The emulsion/AN mixture according to the invention prepared with the low-viscosity emulsion with a high oil content, and especially the preferred "in situ" emulsion,

is particularly suitable for pumping operations. A preferred technique for pumping the mixture into a borehole is to pump it through an annular stream of aqueous lubricating fluid, e.g. naturally occurring water, which flows through the line used to transfer the mixture to the hole. Such a technique is described in US Patent No. (US Patent Application No. 375,543 of May 6, 1982) for pumping a Bingham solid, e.g. a water-in-oil emulsion explosive. When using a method and an apparatus of the type described in said US patent application, the emulsion/AN mixture's resistance to movement through a pipeline can be reduced by providing an annular layer of liquid with low viscosity, e.g. water, around a central column of the mixture in the pipeline. A ring of aqueous lubricating fluid, injected into the pipeline through which the emulsion/AN mixture is to be transported to the borehole, provides sufficient lubrication to allow the column of mixture to slide through the pipeline without undergoing any appreciable deformation due to shear forces, i.e. moving itself in "rod-shaped flow", which is clearly advantageous in terms of maintaining the emulsion structure in the mixture. A further advantage obtained by using this apparatus is that it is more effective when used with small amounts of lubricant, which ensures better regulation of the strength and sensitivity of the explosive mixture due to the reduced risk of dilution. A flow rate of the lubricating liquid that is no higher than 5%, and usually no higher than 0.5 - 2%, of the emulsion/AN mixture flow rate is used.

When pumping is carried out at temperatures above 0°C,

water is the preferred lubricating fluid because water is cheap, has a low viscosity, and is not miscible with the emulsion-AN mixture to be pumped. Additives such as ethylene glycol can be added to the water to lower its freezing point in cold weather. The water does not have to be of high purity or drinkable. Therefore, any naturally occurring water available at the point of use can usually be used, even if such

water, whether it is river water, well water or sea water, always contain a certain amount of dissolved salts.

The method described above where it is used

a ring of lubricant, can be performed with intermittent pumping in periods, if desired, even in the case where water is used as the lubricating fluid. In contrast to the method described in US Patent No. 4,259,977 for pumping emulsions, in the present method - in which the material being pumped is an emulsion filled with solid AN - clogging of the pipeline will not take place when the pumping operation is interrupted , when a water ring is used. It is assumed that year-

the reason for avoiding the problem of swelling/clogging

in the pumping method where a lubricant ring is used, has to do with the nature of the continuous phase in the explosive emulsion used in the present mixture, and more particularly with its hydrophobicity, which is a consequence of the emulsifier or the emulsifier system therein. It is possible that the fatty acid salt, and in particular the equilibrium structure of the emulsifier system produced when the emulsifier is formed in situ, as described in the above-mentioned US Patent No. 4,287,010, provides a unique hydrophobic environment between the lubricating liquid on the outer surface of the emulsion/AN -the mixture and the aqueous phase droplets in the mixture, whereby absorption of the lubricating liquid into the mixture is prevented, despite the presence of a concentration gradient between the lubricating liquid and the aqueous phase droplets. However, it is not necessary to take such concentrations into account when using the present compositions, and any available water may be used as the lubricating liquid.

The method, the emulsion and the emulsion/AN mixtures according to the invention will now be described in more detail by means of examples.

Example 1

The rate of absorption of water into samples of four different emulsions was measured to estimate the relative water transport rates through these emulsions, in emulsion/AN mixtures. The composition of the samples is indicated in the following table. Samples B, C and D, which are samples of emulsions with a low oil content that can be used e.g. in packaged ANFO mixtures according to the invention, was produced according to the method described in example 1 in US Patent No. 4,287,010, with the variations in the mixing speed that will be explained in more detail. The percentages given for oleic acid and ammonium hydroxide represent the proportions that were used in the production of ammonium oleate in situ. Sample A is a sample of an emulsion of the type described in US Patent No. 3,447,978, in which a non-ionic emulsifier is present.

To test the water absorption rate, the samples were filled in cylindrical pans of radius 7.5 mm and height 2.6 mm. The samples were submerged under 25.4 mm of water. With different intervals, a sample was taken out, excess water dried off and the moisture content measured by Karl Fischer analysis. The results are shown in fig. 1.

The effect of cell size on the rate of water absorption into the sample is seen by comparing the curves for C and D, which were the same emulsion mixed at different mixing tipping speeds to produce different viscosity and cell size. The viscosity of C was 1900 poise at 23°C, while the viscosity of D was 4550 poise at 23°C, representing the smallest cell size. Due to its smaller cell size, the aqueous phase in D had a higher chemical potential than the aqueous phase in C, resulting in a lower driving force for water transport into the emulsion. After 3 hours, C had occupied approx. 18% more water than D.

The effect of the type of emulsifier system on the rate of water absorption is more pronounced than the effect of cell size, as will be seen by comparing B, C or D with A. Although A had the smallest cell size of all samples (ie the least chemical driving force for water transport into the emulsion), it absorbed 49% more water than D, obviously as a result of the continuous phase containing the polar, non-ionic emulsifier showing little resistance to water transport.

Example 2

The rate of transfer of water from samples of emulsion A, C and D described in Example 1 to ammonium nitrate pellets in surface contact with the samples was measured to give an estimate of the relative rates of water transport from the discontinuous aqueous phase of the emulsion to AN particles in emulsion/AN - mixtures. In this experiment, where the previously described water diffusion test was used, the emulsion samples according to example 1 were brought into surface contact with a cylindrical ammonium nitrate pellet of the same cross-sectional area. The water that diffused from the emulsion into the AN pellet is indicated as a function of time in fig. 2.

A comparison of samples C and D shows that the smaller cells D increased the driving force for water transport from the emulsion, as sample D had taken 66% more water than sample C after 43 hours. the water loss much higher in A than in C or D

(A had lost 283% more water than C or D after 43 hours), due to the combined hydrophilicity of the continuous

emulsion phase and the higher driving force. A high degree of water absorption in the solid AN results in instability of the emulsion/AN mixture.

Example 3

An emulsion of the following composition was prepared according to the method described in example 1 in US Patent No. 4,287,010:

The percentages given for oleic acid and sodium hydroxide represent the proportions that were used for the production of sodium oleate in situ.

Two mixtures, A and B, were prepared from this emulsion:

A Differential Scanning Calorimeter (DSC) was used to determine the amount of heat released by crystallization of the unmixed emulsion and of the emulsion component of each mixture upon cooling at a rate of 5°K/min from 300°K down to 220°K. These measurements were made when the samples were fresh and after 35 hours of storage at 49°C. Water transport from the emulsion causes concentration of salts in the dispersed aqueous phase and eventually crystallization of the cells. The relative degree of crystallization in each sample before cooling can be estimated through a measurement of the amount of heat released by complete crystallization of the samples by DSC, as a larger amount of released heat corresponds to less crystallization before cooling. The results were as follows:

The above data show that mixture A (the mixture

with ANFO) was 53% more crystallized than the 100% emulsion sample after 35 hours at 49°C. On the other hand, mixture B (the mixture with ANWAX) was only 14% more crystallized and therefore more stable.

Example 4

Emulsion/ANFO mixtures with different component ratios

was prepared by mixing ANFO with an emulsion of the following composition, prepared as described in Example 1 US Patent No. 4,287,010:

The stability of the mixtures after aging was determined by detonating the mixtures with or without confinement and measuring the detonation rate. The results are given in the following table:

Example 5

The following high oil emulsions (22.5 kg) were prepared in a 19 liter mixer by adding a 50% aqueous solution of sodium hydroxide to an aqueous solution of ammonium nitrate at 77°C and adding the base containing aqueous nitrate solution slowly and with stirring to a solution of temperature 30°C of oleic acid in a mixture in the weight ratio 3/1 of fuel oil No. 2 and an oil of quality Gulf Endurance No. 9. The stirrer tip velocity was

133 cm/sec. during the addition of the components and 400 cm/sec. during a subsequent 5 minute shear mixing cycle. The emulsions were then further subjected to shear mixing to reduce the cell size sufficiently to produce a viscosity comparable to that obtainable by mixing at 600 cm/sec. for another 2 minutes.

With addition for formation of oleate emulsifier in situ.

Emulsions A through E (at ambient temperature) were mixed with AN beads to form mixtures A through E. The mixing operation was performed in a cement mixer at medium speed for 4 minutes.

A typical emulsion that would be mixed in the same way as emulsions A-E above is made from the following ingredients:

Example 6

The importance of larger amounts of emulsifier in emulsions with a high oil content determined by the production of the following emulsions in 700 g quantities according to the method described in example 5, except that the shear mixing operation at 400 cm/sec. was performed in just 1 minute. When necessary, the duration of shear mixing was changed to give the emulsion a viscosity of 1000 poise. The emulsion stability was measured by centrifuging the emulsion for 10 minutes at 2500 rpm. minute every day for 3 days, at the ambient temperature, and determination of the weight loss from the continuous (olhe) phase.

Example 7

The stability of the viscosity of mixtures of AN beads with the high oil emulsion according to the invention, compared to the stability of the viscosity of mixtures prepared using high oil emulsions but containing nonionic emulsifiers in sufficient amounts to preserve emulsion stability, was shown by measured the viscosity of six emulsion/bead mixtures containing 37.6 wt% AN beads and 62.4 wt% emulsion. Three emulsions (K, L and M) were according to the invention and contained different amounts of emulsifier, all amounts being sufficient to form a stable emulsion. Three emulsions (N, 0 and P) were control emulsions with high oil content (i.e.

they contained a sufficient amount of oil to provide oxygen balance in the mixture with AN beads) which contained a non-ionic emulsifier in three different concentrations. Only two of these concentrations (in emulsions 0 and P) were sufficient - to prevent "cream formation" in the oil phase.

In these emulsions, the aqueous phase was a solution consisting of 696 wt% ammonium nitrate, 15.5 wt% sodium nitrate (SN) and 14.9 wt% water. Emulsions K, L and M were prepared according to the method described in example 6 (except that SN was incorporated in the aqueous phase). Emulsions M, 0 and P were prepared by adding sorbitan monooleate to the oil and the AN/SN solution to the oil solution.

In the preparation of all six emulsions, the extender spheres ("extendospheres") (consisting of fly ash) were added during the addition of the AN/SN solution to the oil. The emulsion viscosity was measured with a Brookfield viscometer at 29°C using a Type E spindle with a rotation speed of 2 rpm.

The mixtures were prepared by mixing the emulsion and AN beads together using low shear forces, namely by hand with a spatula.

The results are given in the following table and are listed in the diagram in fig. 3.

The viscosity was measured (as described for the emulsion, except that it was measured at 25°C) for freshly prepared mixtures and for two and six day old mixtures. Curves showing the viscosity deposited as a function of time are shown in fig. 3 for mixtures K - P. All mixtures had an initial viscosity in the range 12,000 - 4,000 poise. While the compositions according to the invention, i.e., compositions K, L and M, showed only a moderate increase in viscosity over a six day period, the viscosity reaching only 4500-5000 poise after six days, the control compositions O and P showed a rapid increase during just two days. Control mixture N, which was prepared from emulsion N, and which had an SMO concentration

tion which was so low that it was insufficient to create

maintaining emulsion stability, showed a low viscosity increase over a two day period, but showed a rapid viscosity increase over the next four days. The extremely high viscosities of control mixtures 0 and P after two days rendered the mixtures practically non-pumpable (more precisely, unable to

flow by gravity from a tank to the suction side of a pump) and indicated a detrimental change in the emulsion structure (crystallization in the water phase) that characteristically compromises the mixture's ability to detonate. In contrast, mixtures K, L and M showed no visible signs of crystallization and were suitable for pumping.

Example 8

The following experiment shows that stable emulsion/ANFO mixtures according to the invention, which exhibit minimal water transport, can be improved by using the emulsion according to the invention with a high content of oil and a high content of emulsifier.

Three emulsions, Q, R and S, were prepared as described in

example 5 for the production of emulsions A-E (except that in emulsions Q and R sodium nitrate was incorporated in the aqueous phase, as in example 7). Emulsions R and S were the preferred emulsions with a high oil content, and emulsion Q

was an oxygen-balanced emulsion with a lower oil content and a lower emulsifier content than emulsions R and S. Blends R and S were 50/50 mixtures of emulsion AN beads. Emulsion Q was mixed in the same ratio with ANFO beads,

i.e. AN beads that had been lightly coated with fuel oil

in a weight ratio AN/oil of 94/6. The mixing operation was carried out in a cement mixer as described in example 5. The results were as follows:

The detonation velocity (m/sec.) was measured for unconfined samples of diameter 12.7 cm which were initiated with a 0.45 kg detonator. Although Mixture Q is comparable to Mixtures R and S after aging for 39 days in terms of confined space detonation velocity, Mixtures R and S require no containment at this age (nor does Mixture S at age 60 days) to detonate with satisfactory speed.

Claims (26)

1. Process for the production of an explosive, in which particles of ammonium nitrate (AN) are combined with a water-in-oil emulsion comprising (a) a liquid carbonaceous fuel whose components form a continuous emulsion phase, (b) an aqueous solution of a inorganic oxidizing salt which forms a discontinuous emulsion phase dispersed as separate small droplets in the continuous phase, and (c) an emulsifier which forms a mixture of said particles and the emulsion, containing a sensitizing amount of dispersed gas bubbles or voids, characterized in that the AN particles and the components of the emulsion form a structure which minimizes the loss of water from the aforementioned small droplets and the transfer of the water through the continuous oil phase to the AN particles. 2. Method according to claim 1, characterized in that the mixture is packaged after it has been formed. 3. Method according to claim 1, characterized in that the structure is formed by combining the AN particles with an emulsion which, in the emulsifier system, contains a salt of a fatty acid in addition to the free fatty acid dissolved in an oil, the oil solution forming the continuous emulsion phase, while the fatty acid, the fatty acid salt and the oil together form the liquid, carbonaceous fuels. 4. Method according to claim 3, characterized in that the fatty acid is selected from saturated and mono-, di- and tri-unsaturated monocarboxylic acids containing from 12 to 22 carbon atoms, and that the salt is an alkali metal, ammonium and/or alkylammonium salt. 5. Method according to claim 4, characterized in that the structure is formed by combining the AN particles with an emulsion which has been obtained by bringing together the oil and the aqueous solution while stirring in the presence of the fatty acid and a base, so that the fatty acid salt emulsifier has been formed in situ. 6. Method according to claim 4, characterized in that AN beads are combined with an emulsion containing liquid, carbonaceous fuel in an amount sufficient to provide substantially full oxygen balance to the AN beads and the inorganic oxidizing salt present in the aqueous solution, and that the AN beads constitutes from 20 to 70% by weight of the mixture. 7. Method according to claim 6, characterized in that the structure is formed by combining the AN beads with an emulsion which has been obtained by bringing the oil and the aqueous solution together while stirring in the presence of a fatty acid and a base to form the fatty acid salt emulsifier in situ. 8. Method according to claim 7, characterized in that the amount of liquid, carbonaceous fuel in the emulsion is from 7 to 21%, calculated on the weight of the emulsion. 9. Method according to claim 8, characterized in that the amounts of fatty acid and base that are added to form the fatty acid salt in situ are sufficient so that the weight ratio between the added oil and the added fatty acid is in the range from 1/1 to 3/1, and that the equivalence ratio between the amount of added base and the amount of added fatty acid is in the range from 0.5/1 to 3/1. 10. Method according to claim 9, characterized in that the fatty acid is oleic acid, and that the fatty acid salt is ammonium oleate and/or one or more alkali metal salts of oleic acid. 11. Method according to claim 1, characterized in that the structure is formed by the particles and the emulsion being mixed with each other at a mixing speed and for a time sufficient to form a cell size in the discontinuous emulsion phase which is in the range from 1 to 4 µm. 12. Method according to claim 1, characterized in that the structure is formed by coating the AN particles with an agent in which water has a diffusion coefficient at 25°C that is lower than 10 cm/sec. 13. Aged, storage-stable explosive comprising, in a pack, a mixture of at least 30% by weight of ammonium nitrate (AN) particles and at least 30% by weight of an emulsion comprising (a) a liquid carbonaceous fuel including an oil solution of a fatty acid , which solution forms a continuous emulsion phase, (b) an aqueous solution of an inorganic oxidizing salt which forms a discontinuous emulsion phase dispersed as separate small droplets in the continuous phase, and (c) an emulsifier system including an emulsifier comprising (1) an alkali metal- , ammonium or alkylammonium salt of a fatty acid containing from 12 to 22 carbon atoms and (2) the free fatty acid, the fatty acid, the fatty acid salt and the oil together forming the liquid, carbonaceous fuel, the mixture containing dispersed gas bubbles or voids constituting at least 5% of the mixture volume, and the emulsion, after aging at 25°C for two days, does not lose more than 4% of its original weight when it is subjected to the described water diffusion test. 14. Explosives according to claim 13, characterized in that the emulsion has been produced by bringing together the aqueous solution and an oil while stirring in the presence of a fatty acid and a base to form the fatty acid salt in situ, and that the emulsification system also contains a base. 15. Water-in-oil emulsion adapted for mixing with ammonium nitrate beads to form an explosive, characterized in that the emulsion comprises: (a) from 7 to 21% by weight of a liquid carbonaceous fuel comprising an oil solution of a fatty acid, which solution forms a continuous oil phase, (b) an aqueous solution of an inorganic oxidizing salt forming a discontinuous emulsion phase dispersed as separate small droplets in the continuous phase, and (c) an emulsifier system comprising (1) said fatty acid and (2) a fatty acid salt, the oil, the fatty acid and the fatty acid salt together forming the liquid carbonaceous fuel, and that the weight ratio between the amounts of oil and fatty acid supplied to form the emulsion is in the range from 1/1 to 3/1, which emulsion has an oxygen balance that is more negative than -6%. 16. Emulsion according to claim 15, characterized in that the emulsifier system is an emulsifier system which is formed in situ from a fatty acid and a base when the oil and the aqueous solution are brought together to form the emulsion, that the equivalence ratio between the amount of base and the amount of fatty acid added to form the emulsifier system is from 0, 5/1 to 3/1, and the emulsion has a viscosity in the range from 500 to 10,000 poise and has a stable emulsion structure for at least three months. 17. Emulsion according to claim 15, characterized in that the emulsifier system is formed by the addition of a fatty acid and a salt of a fatty acid to the other components of the emulsion, the quantity ratio between oil and "fatty acid" being understood as the ratio between oil and fatty acid plus fatty acid salt added during the preparation of the emulsion, and the ratio between added fatty acid salt and added fatty acid is at least 0.5/1. 18. Emulsion according to claim 15, character, ized. in that the fatty acid salt is selected from alkali metal, ammonium and alkylammonium salts of saturated and mono-, di- and tri-unsaturated monocarboxylic acids containing from 12 to 22 carbon atoms. 19. Emulsion according to claim 18, characterized in that the fatty acid is oleic acid, and that the fatty acid salt is ammonium oleate and/or one or more alkali metal salts of oleic acid. 20. Emulsion according to claim 15, characterized in that it practically contains no dispersed, airborne solid material. 21. Explosives, characterized in that it comprises a mixture of 30 - 80% by weight of the emulsion according to claim 15 and 70 - 20% by weight ammonium nitrate beads, the amount of ammonium nitrate beads being sufficient to give the emulsion a practically full oxygen balance, and that the mixture contains a sensitizing amount of dispersed gas bubbles or cavities. 22. Explosives, characterized in that it comprises a mixture of 50 - 80% by weight of the emulsion according to claim 16 and 50 - 20% by weight of ammonium nitrate beads, the amount of ammonium nitrate beads being sufficient to give the emulsion a practically full oxygen balance, and that the mixture contains a sensitizing amount of dispersed gas bubbles or voids, has a viscosity in the range of 2500 to 20,000 poise and maintains a viscosity in this range for several days. 23. Explosive according to claim 21, characterized in that the dispersed gas is the gas that is present in the ammonium nitrate beads. 24. Explosives according to claim 21, characterized by the fact that it also contains others air-bearing solid materials. 25 . Method of delivering the explosive according to claim 22 to the borehole, through a pipeline, characterized in that the explosive is pumped to the borehole through an annular flow of an aqueous lubricating liquid which flows through the pipeline in the same direction as the explosive, and that the explosive is adapted so that the flow resumes when pumping resumes after a longer period of rest in the pipeline, regardless of the composition of the aqueous lubricating fluid. 26. Method according to claim 25, characterized in that the aqueous lubricating liquid is naturally occurring water.