The present invention relates to an explosive. More particularly, the invention relates to a water-in-oil type emulsion explosive utilized for industrial blasting operation such as excavating tunnels, quarrying and mining.

With respect to the industrial explosive used for blasting operation, such as dynamites, watergel explosives, ammonium nitrate explosives and ammonium nitrate-fuel oil explosives (hereinafter referred to as ANFO explosives) are well-known in the art. Among those explosives, water-gel explosives, without comprising gunpowder as a component, are considered to be safer in comparison with the conventional dynamites and are widely employed as industrial explosives. Said water-gel explosive, being categorized into two types of explosives such as slurry explosives and emulsion explosives, the emulsion types are characterized as being excellent in formability and weather resistance. Since the first disclosure of a water-in-oil type emulsion explosives in United states Patent No.3,161,551, various improvements have been made. And now it became possible to obtain the explosives excellent in water-resistance and safety which never given in to the conventional ones.

On the other hand, mechanization of explosive charging is come to be on demand at a blasting site from the view points of facilitation in charging and safety in dealing with explosives. The explosives being required to be safer in the mechanical charge operation, the method for charging ANFO explosives with mechanical charging equipment such as loader has come into practice at quarry and mine. Whereas, in comparison with emulsion explosives, ANFO explosives require an adequate exhaust system due to the noxious residual gas compositions generated during blasting. When used under conditions where water is present in a blast hole, ANFO explosives, being dissolved in water, fail to exhibit an intended explosive performance, and consequently become difficult to be used. The charging of a blast hole or a spring hole containing water with an ANFO explosive may require such annoying steps; firstly drain a blast hole before fitting poly-tube into it, secondly place a poly-tube in a blast hole, and finally charge a poly tube with ANFO explosives. For example in overseas, Bulk Emulsion Blasting System, where charging of blast hole with water-in-oil type emulsion explosives called bulk emulsion explosives is conducted directly and automatically by using air drive mono-pump by the method according to "Investigation Report for Effective Tunneling Technology"; issue of Japan Tunneling Association (JTA), has come into a practical use. Bulk Emulsion Blasting System, where thick water-in-oil type emulsion explosives are used, incurs high cost due to derived annoyances such as cleaning after charging operation or maintenance for left-over explosives. Charging with bulk emulsion explosives also requires costly mechanical charging equipment for safety's sake.

What is thus desired is an explosive with high-security, that can be charged with a rather simple mechanical equipment such as a pneumatic loader and can be used even in a relatively watery blast hole. In order to solve such problems, the development of water-in-oil type emulsion explosives in granulated or particulate form disclosed in JP Laid-Open Nos.223888/1995 and 278975/1999 has been carried out.

Whereas, the granulating method disclosed in the above publications is carried out by firstly breaking down the emulsion structure with crystallization of an inorganic aqueous oxidizer solution within the emulsion, thereby bringing into the particulate form.

It is generally known that the crystallization of an aqueous oxidizer solution in water-in-oil type emulsion explosives incurs deformation of emulsion setting out from said crystallization site, which results in loss of sensitivity or performance with the explosives. Even for explosives of such operation, it is not a big problem because explosives only need to be stored in such a short time as several hours or several days from the time of production before using, if so-called "site mixing method" or a similar method is applicable. It often be the case, though, the period from the production of the explosive to use is generally a few months or, if longer, about six months to about one year. Therefore, it is required even for the water-in-oil type emulsion explosive in a granular or particulate form to have good stability in lapse of time over several months free from crystallization of aqueous oxidizer solution therein. It is particularly desired for the water-in-oil type emulsion explosive to remain stable without loosing its properties in order to allow mechanical charge.

The explosive formed into granules, if stored long under a load with mechanical charge or so, agents thereof getting agglomerated and not being disagglomerated when using, occasionally becomes difficult to be managed to use. Because of this, it is desired for the water-in-oil type emulsion explosive in a particulate form to be not agglomerated or, if agglomerated, to be easily disagglomerated even after a long-term storage under a load with mechanical charge or so.

The present inventors made a diligent study in order to solve above problems and consequently have completed the present invention by finding out it is obtainable that the solid explosives i.e. water-in-oil type emulsion explosive strong enough and stable for over several months, when continuous phase components of water-in-oil type emulsion are replaced entirely or partially by ethylene vinyl acetate copolymers; or when ethylene vinyl acetate copolymers are included therein.

Namely, the present invention relate to,

• (1) A water-in-oil emulsion type explosive characterized by having a continuous phase comprising ethylene vinyl acetate copolymers;
• (2) The water-in-oil emulsion type explosive according to the above (1), characterized by comprising ethylene vinyl acetate copolymers from 0.2 to 8 % by mass of total amount of the explosive;
• (3) The water-in-oil type emulsion explosive characterized by comprising oxidizers, oily materials, ethylene vinyl acetate copolymers, emulsifiers and hollow microspheres;
• (4) The emulsion explosive according to the above (3), wherein hollow microspheres are glass microbaloons or resin micorbaloons;
• (5) The emulsion explosive according to the above (3), wherein comprising 30 % by mass or more of ethylene vinyl acetate copolymers to the total mass of oily materials and ethylene vinyl acetate copolymers;
• (6) The emulsion explosive according to the above (3), wherein the melt-flow rate of ethylene vinyl acetate copolymers is 10 g / 10 min. or more;
• (7) The emulsion explosive according to the above (3), wherein a number average molecular weight of ethylene vinyl acetate copolymers is 100 to 50,000 Mn;
• (8) The emulsion explosive according to any one of above (1) to (7), wherein the emulsion explosive is characterized as solid;
• (9) The explosive according to the above (8), formed into a columnar shape of from 3 to 20 mm in diameter and from 1 to 30 mm in length.

The present invention will be described below in more details. "Part" and "%" hereinafter in the description are indicated by mass unless otherwise specified.

A continuous phase in the water-in-oil type emulsion explosive according to the present is an oil phase (fuel phase), wherein generally preferred is a mixture containing both oily materials and ethylene vinyl acetate copolymers (hereinafter, may be called EVA resins). An oil phase as being the continuous phase of the present invention may not always contain the oily materials, may be formed of EVA resins or a resin mixture of said EVA resins and other resins.

EVA resins, having a property to be cured or weakened in its viscosity by heating, are preferred to be molded by injection when made into a mixture of oxidizers, water, emulsifiers and hollow microspheres as well as oily materials as needed. More specifically, EVA resins generally used are of a number average molecular weight ranging from 100 to 60,000 Mn, preferably are of said molecular weight ranging from 100 to 50,000 Mn. More preferably are of the said molecular weight of 2,000 Mn or more, still more preferably are of within the range from 10,000 to 40,000 Mn.

EVA resins used in the present invention may be copolymers comprising other copolymer compositions as far as ethylene vinyl acetate copolymers are included as a principal composition. When EVA resin is copolymers comprising other copolymers, preferably includes from 30% to 100% of ethylene vinyl acetate copolymers relative to the entire EVA resin, more preferably from 50% to 100%, still more preferably from 70% to 100%. Most preferably is an ethylene vinyl acetate copolymer substantially including no other copolymers as constituents thereof. The ratio of ethylene and vinyl acetate are not particularly limited as far as it is an ethylene vinyl acetate copolymer, however, generally preferred is vinyl acetate: ethylene = 1:9 to 1:15 in molar ratio.

Ethylene vinyl acetate copolymers may be included in the amount sufficient enough to carry out the present invention effectively, preferably be included 0.2% or more to the total amount of the present explosive, more preferably 0.4% or more, still more preferably 0.6% or more, and 8% or less, more preferably 6% or less, still more preferably 4% or less. The most preferable range, though varies depending on the types ofthe ethylene vinyl acetate, generally is approximately from 0.6 to 3%.

The continuous phase in the present invention is preferably a mixture including oily materials and ethylene vinyl acetate copolymers as described below. The resins included in the continuous phase may solely be EVA resin, however, resins other than ethylene vinyl acetate copolymers may also be included as long as the present invention can be carried out effectively. Other resins may preferably show oil solubility or compatibility with oily materials.

Said other resins include heat-curable resins, thermoplastic resins and synthetic rubbers or so. To be more specific, sulfurated rubbers, petroleum resins, phenol resins, AAS resins, ABS resins, PET resins, urea resins, melamine resins, epoxy resins, unsaturated polyester resins, polyurethane resins, polyvinyl chlorides, polyvinyl acetates, polyamide resins, polyimide resins and polyethylene resins are included, however, to keep stability of water-in-oil type emulsion explosive, the resins showing no reactivity with other components are preferred. Also, the heat-curable resins that is liquid at room temperature or low in melting point and the thermoplastic resins that is solid at room temperature showing flowing property when heated are preferable. Examples of those include such as phenol resins, petroleum resins, polyethylene, polypropylene, polybutene, polyisobutylene, ethylene vinyl acetate copolymer resins, polybutadiene and styrene-butadiene rubbers, preferably include petroleum resins and ethylene vinyl acetate copolymer resins. Among the above, petroleum resins, optionally being hydrogenerated, such as an aliphatic or C₅-petroleum resins obtained from C₅ -fractions of cracked oil, an aromatic or C₉-petroleum resin obtained from C₉-fractions or C₅ C₉ copolymerized petroleum resins obtained from both fractions can be used. Examples of resins obtained from C₅-fractions include copolymers such as isoprene, piperylene, 2-methylbutene-1 and 2; conjugated diolefin usually having a ring structure, the representative structure thereof is shown generally by the following formula:

The resins obtained from C₉-fractions are copolymers comprising such as styrene, vinyl toluene, α-metylstyrene and indene as main components which is generally shown by the following formula:

The term "an oil mixture" used in the description of the present invention, means a mixture of EVA resins and oil materials or/and EVA resins, unless otherwise specified.

In the present invention, the continuous phase is formed of an oil mixture. The percentage of EVA resin to the total content of oil materials and EVA resins is not particularly limited as far as the present invention is carried out effectively, but usually is 10% or more, preferably is 20% or more; an oil mixture as a whole can be EVA resins depending on the cases. More preferably, however, EVA resins are included from 30% to 80% to the total content of an oil mixture. When used with other resins, it is preferred that EVA resins are included in the same percentage or more than the above described lower limit, making the total of EVA resins and other resins to be in the same or less than the above upper limit. The preferable content of EVA resins varies more or less depending on the molecular weight thereof, EVA resins of high molecular weight may be inclined less in the amount, whereas EVA resins of lower molecular weight may comparatively be included more. For example, when a number average molecular weight is 10, 000 or more, preferably 12,000 or more, more preferably 20,000 or more, the content thereof may be 60% or less, preferably from 25% to 50% to the above total content. EVA resin of lower molecular weight, of which number average molecular weight is more or less from 2,000 to 3,000, the content thereof may be 50% or more, more preferably from 60% to 80%, more or less.

EVA resins, which is usually used in a molten state in the process of producing the oil-in-water type emulsion explosive of the present invention, preferably melts at producing temperature. For example, it is desired to use EVA resins of which melt-flow rate measured according to "Flow test method for thermoplastics resin" (JIS K7210) is 10 g / 10 min. or more, preferably 15 g / 10 min. or more.

For other resins if used together with EVA resins, the same condition as above is applicable.

A number average molecular weight of resins can be measured by gel permeation chromatography or so.

The explosive of the present invention usually includes oily materials. Oily materials, which are generally used for the water-in-oil type emulsion explosives can be utilized. Oily materials, enhancing the emulsification property of emulsion, form the continuous phase with EVA resin. Examples of the oily materials include petroleum oils such as diesel oil, coal oil, mineral oil, grease and crude oil; petroleum waxes such as paraffin wax and microcrystalline wax; and other oily materials such as hydrophobic vegetable oils, vegetable waxes, animal oils and animal waxes, those which may be employed solely or in combination of two types or more.

The oil mixture of the present invention comprising oily materials, is included in the explosive usually in the range from 0.1% to 20%, preferably in the range from 1% to 10%. In one preferable embodiment of the present invention, when the resin having a number average molecular weight from 100 to 50,000 are used, the amount of oil mixture used in the explosives is generally 0.1% or more to the total content, preferably 0.5% or more, more preferably 1% or more, still more preferably 1.5% or more. The upper limit thereof is generally about 10%, preferably is 7% or less. The most preferable range is from about 2% to about 5 %, more or less.

The emulsifiers used in the explosive of the present invention include the emulsifiers generally used in the oil-in-water type emulsion explosive, examples of those include fatty acid salts having about 15 to about 30 carbon atoms such as alkali metal stearate, ammonium stearate and calcium stearate (preferred are alkali metal, alkaline earth metal and ammonium salt, and the like); polyoxyethylene ethers; fatty acid esters; preferably fatty acid esters having 15 to 30 carbon atoms such as sorbitan fatty acid ester and sorbitol fatty acid ester. Those are used as a mixture of one type, or two types or more. The amount of emulsifiers used in the explosives is 0.1% or more to the total content, preferably 0.5% or more, more preferably 1% or more, the upper limit thereof is generally about 10%, preferably 7% or less, more preferably 5% or less.

The oxidizers used in the explosives of the present invention are preferably in the form of aqueous solution thereof. The oxidizers include nitrate salts or perchlorates, the specific examples of those include alkali metal nitrates such as sodium nitrate; alkaline earth metal nitrates such as calcium nitrate; alkali metal chlorates such as ammonium nitrate or sodium chlorate; alkaline earth metal chlorates such as calcium chlorate; alkali metal perchlorates such as potasium perchlorate; alkaline earth metal perchlorates such as calcium perchlorate; and ammonium perchlorates. They may be used solely or in combination of two types or more. The most preferable oxidizers among them are ammonium nitrate and sodium nitrate. As described infra, it is preferred that the content of oxidizer in the aqueous oxidizer solution is suitably adjusted according to the intended use such that the crystallization temperature of said aqueous solution is to be from 30°C to 90°C. Accordingly, though varies depending on the types of oxidizers, the content thereof ranges generally from 60% to 95%, preferably from 70% to 93%, more preferably from 85% to 92%.

To the aqueous oxidizer solution of the present invention, auxiliary sensitizers can be added if desired, examples of those include water-soluble amine nitrates such as monomethylamine nitrate, monoethylamine nitrate, hydrazine nitrate and dimethyamine dinitrate; water-soluble alkanolamine nitrates such as methanolamine nitrate and ethanolamine nitrate; and water-soluble ethylene glycol mononitrates.

The aqueous oxidizer solution used in the present invention preferably adjusted upon necessity such that the crystallization temperature of said aqueous solution is to be from 30°C to 90°C. The content of water in the aqueous oxidizer solution to said entire solution is generally ranges from 5% to 40%, preferably from 7% to 30%, particularly preferred is from 8% to 15%. In order to reduce crystallization temperature of aqueous oxidizer solution, water-soluble organic solvents such as methanol, ethanol, formamide, ethylene glycol, glycerol may be used as auxiliary solvents. The aqueous oxidizer solution ( the auxiliary solvents may also be included depending on the cases ) in the explosive of the present invention, being a residue remained excluding other components thereof, is preferably included in the range from 60% to 97% to the total content of the explosive, more preferably from 80% to 95%.

The sensitivity of the explosive can be adjusted in a broad range from cap initiation to booster initiation by adding suitable amount of density reducing agents, which are preferably hollow microspheres, into the composition of the water-in-oil type emulsion explosive of the present invention. The density reducing agents generally used is 0.8 g/cc or less in density, preferably 0.5 g/cc or less, more preferably 0.3 g/cc or less. With respect to the organic agents, the density is 0.1 g/cc or less, or the agents of its density 0.05 g/cc or less can also be used depending on the cases. The density reducing agents may include any substances as long as they are inactive and low in density, however, hollow microspheres are preferable to obtain a stable explosive property. As hollow microspheres, for example, inorganic hollow spheres such as glass microbaloons and silastic microbaloons; and organic hollow spheres such as styrofoams and resin microbaloons are used as a mixture of one or two types or more; glass microbaloons or resin microbaloons are preferable and glass microbaloons are the most preferable. Amount for use of density reducing agents may vary in a broad range depending on the intended use of the explosives and also depending on the relative density of hollow microspheres, however, those are used generally in the amount that the density of the explosive remains 0.8 g/cc or more, preferably 0.9 g/cc or more, more preferably 1 g/cc or more; 1.4g/cc or less, preferably 1.3 g/cc or less. The preferable percentage to include the density reducing agents ranges from about 0.1% to about 10% to the total amount of the explosives, more preferably from 1% to 8%, still more preferably from 1% to 6%; the most suitable range is from 2% to 10% depending on the cases. In the case of glass microbaloons, which is a preferable embodiment of the present invention, the preferable percentage is 1% or more; 2% or more depending on the cases, 8% or less, more preferably 5% or less.

Metal powders such as pulverized aluminum and pulverized magnesium; and powdery organic materials such as wood powder and starch can also be added to the explosives of the present invention. The amount added to the explosives ranges from 0% to 10%, though depending on the types of agents and the intended use thereof.

The explosive of the present invention, for example, is produced by the following method.

Namely, the above described oxidizer and the above described auxiliary sensitizer, if desired, are dissolved in water at about 85°C to 95°C to obtain the aqueous oxidizer solution. Additionally, oil mixture compositions (e.g. EVA resins and oily materials, if desired, other resins than EVA resins) and emulsifiers are mixed thoroughly under the condition molten by heating to obtain the oil mixture including emulsifiers. Then, to the said oil mixture heated at about 85°C to 95°C, the above aqueous oxidizer solution is added gradually under stirring thoroughly to obtain a base material for the water-in-oil type emulsion explosive. Consequently, the density reducing agents such as hollow microspheres and other additives, if desired, are added to the said water-in-oil type emulsion keeping the above temperature, followed by mixing by kneader to obtain the water-in-oil type emulsion explosives of the present invention. The obtained explosive is transferred to molding machine while still flowing or after cooled to the room temperature, followed by molding to obtain the molded explosive of the present invention. A part of oil mixture compositions may be added as well with hollow microspheres when obtaining the water-in-oil type emulsion. For example, oily materials and emulsifiers may be mixed at first to obtain water-in-oil type emulsion, then EVA resins may be added thereto and mixed at the same time when hollow microspheres are added; or EVA resins and emulsifiers may be mixed at first to obtain water-in-oil type emulsion, then oily materials may be added thereto and mixed at the same time when hollow microspheres are added; generally however, it is preferable that oil mixture compositions and emulsifiers are mixed at first to obtain water-in-oil type emulsion as an oil mixture including emulsifiers, followed by added thereto the hollow microspheres.

Thus obtained water-in-oil type emulsion explosives of the present invention are preferably molded into suitable shape by the conventional method for use. There is no particular limitation to the molded shape of the present explosive, they may be molded into any shapes such as spherical shape, cylindrical shape, disk shape or rectangular column shape depending on the molding machines to be used. The explosive may be molded into any shapes, however, the size thereof is preferably 30 mm or less in the maximum length within its shape ( the length of the longest side or maximum diameter in its shape), more preferably 20 mm or less; whereas the minimum length ( the length of the shortest side or minimum diameter in its shape) is preferably 1 mm or more, more preferably 3 mm or more.

The method of producing the present invention includes the conventional method using extruder or the method wherein the water-in-oil type emulsion explosives are crushed or grinded by a grinding machine or so and then formed into granular by granulator. However, the extrusion method is preferable because the latter method involves intricate steps. To be more specific, the water-in-oil type emulsion explosive is extruded through a hole-plate or screen to obtain pole-shaped explosive, followed by cutting it into suitable length by knives or wires to obtain the explosive in columnar shape. In the molded explosive of the present invention, if the size thereof is too big, void ratio increases and thereby results in lesser propagation of detonation when loaded in a blast hole, the size is from 3 mm to 20 mm in diameter, from 1 mm to 30 mm in length, preferably from 5 mm to 10 mm in diameter, from 3 mm to 20 mm in length, more or less.

The explosive of the present invention formed into a cylindrical shape can be produced by a simple method such as the conventional method for producing the water-in-oil type emulsion explosive.

The present invention will now be illustrated in a more detail by way of the following Examples although the present invention is never limited thereto.

The aqueous oxidizer solution comprising 75.0 parts of ammonium nitrate, 4.8 parts of sodium nitrate and 10.6 parts of water at 90°C was added to the mixture of 1.5 parts of microcrystalline wax, 1.4 part of ethylene-vinyl acetate copolymer (EVAFLEX P-2807; a number average molecular weight of 20,000 - 30,000 Mn; melt-flow rate:15 g / 10 min.; made by Du Pont-Mitsui Polychmicals Co., Ltd. ) and 2.9 parts of sorbitanmonooleate, followed by stirring and mixing thoroughly to obtain a water-in-oil type emulsion. Thereto added 3.8 parts (density : 0.25 g/cc) of glass microbaloons as hollow microspheres and stirred and mixed to obtain the water-in-oil type emulsion explosive of the present invention. The water-in-oil type emulsion explosive was molded into shape by extruder with dies of 8 mm in diameter, followed by cutting by knife in length of 10 mm to obtain the explosive of the present invention. The density of obtained explosive was 1.17.

The aqueous oxidizer solution comprising 75.0 parts of ammonium nitrate, 4.8 parts of sodium nitrate and 10.6 parts of water at 90°C was added to the mixture of 1.5 parts of microcrystalline wax, 1.4 part of ethylene-vinyl acetate copolymer (Ultracen 720; a number average molecular weight of about 37,000 Mn; melt- flow rate: 150 g /10 min.; made by Tosoh Corporation) and 2.9 parts of sorbitanmonooleate, followed by stirring and mixing thoroughly to obtain a water-in-oil type emulsion. Thereto added 3.8 parts (density : 0.25 g/cc) of glass microbaloons as hollow microspheres and stirred and mixed to obtain the water-in-oil type emulsion explosive of the present invention. The water-in-oil type emulsion explosive was molded into shape by extruder with dies of 8 mm in diameter, followed by cutting by knife in length of 10 mm to obtain the explosive of the present invention. The density of obtained explosive was 1.17.

The aqueous oxidizer solution comprising 75.0 parts of ammonium nitrate, 4.8 parts of sodium nitrate and 10.6 parts of water at 90°C was added to the mixture of 3.8 parts of microcrystalline wax and 2.0 parts of sorbitanmonooleate, followed by stirring and mixing thoroughly to obtain a water-in-oil type emulsion. Thereto added 3.8 parts (density : 0.25 g/cc) of glass microbaloons same as Examples as hollow microspheres and stirred and mixed to obtain the water-in-oil type emulsion explosive for the comparison. The water-in-oil type emulsion explosive was molded into shape by extruder with dies of 8 mm in diameter, followed by cutting by knife in length of 10 mm to obtain the explosive for the comparison. The density of obtained explosive was 1.17.

The composition ratio of each oil-in-water type emulsion explosive obtained in Examples 1 to 3 and Comparative example 1 is shown in Table 1. Composition ratio

Example 1 Example 2 Comparative

Example 1 ammonium nitrate 75.0 75.0 75.0 sodium nitrate 4.8 4.8 4.8 water 10.6 10.6 10.6 microcrystalline wax 1.5 1.5 3.8 sorbitanmonooleate 2.9 2.9 2.0 EVAFLEX P-2807 1.4 - - Ultracen 720 - 1.4 - glass microbaloons 3.8 3.8 3.8

The explosives obtained in Examples 1 to 2 and Comparative example 1 were charged with a pneumatic loader into a steal pipe with inner diameter of 48 mm, 1m in length, 5 mm in wall thickness, followed by initiated by using 50 g of watergel explosive (trade name: Altex) made by Nippon Kayaku Co., Ltd. as a booster, then determined the detonation velocity by d'Autriche method.

Each explosive was charged with a pneumatic loader into the same steal pipe, which was filled with water beforehand, in the same way as the above and also determined the detonation velocity.

Further, for the storage test, the molded explosives obtained above have been placed in vinyl bags in thickness of 15 to 20 cm and stored for 6 months / 1 year respectively. The detonation velocities were measured respectively in both dry and wet pipes by using the same method as above. The results are shown in Table 2.

In order to test the agglomeration property of the explosives under a load and easiness in disagglomeration, 20Kg each of explosives obtained in Examples 1 - 2 and Comparative example 1 was packaged practically (placed in bag and packaged in cardbord box) and has been stored as it was for 6 months / 1 year at room temperature respectively. The status of the explosives after storage of 6 months / 1 year has been observed and evaluated. The results of the test are shown in Table 2. Results of Performance Test Example 1 Example 2 Comparative

Example 1 detonation velocity

(m/s) elapsed time forthwith after production dry hole 2824 2970 3120 watery hole 3110 3210 3430 6 months after dry hole 2970 2890 impposible to be determined watery hole 3280 3190 impposible to be determined 1 year after dry hole 2930 3030 impposible to be determined watery hole 3220 3300 impposible to be determined solidification elapsed time 6 months after slight partial agglomeration slight partial agglomeration agglomerated 1 year after slight partial agglomeration slight partial agglomeration agglomerated easiness in disagglomeration elapsed time 6 months after Easy easy difficult 1 year after Easy easy difficult

As shown in Table 2, the explosives of the present invention, showing no agglomeration, have maintained the initial feature and performance after one-year storage under un-loaded condition at room temperature. Contrary to the above, the detonation velocity forthwith after the production can be determined with reference to the explosives of Comparative example, however, the explosives get agglomerated after 6 months of storage even under un-loaded condition. The detonation velocity, therefore, was not able to be determined as shown in Table 2.

Further, with reference to the agglomeration property under a load, the explosives of the present invention showed partial and slight agglomeration in both 6 months and 1 year of storage. However, the agglomeration thereof came apart easily with a slight impact, there had been no problem in charging with charging equipment. However, the explosives of the Comparative example got agglomerated to the extent that could hardly be disagglomerated after both 6 months / 1 year of storage, whereby it was difficult to be charged with charging equipment.

The aqueous oxidizer solution comprising 75.0 parts of ammonium nitrate, 4.8 parts of sodium nitrate and 10.6 parts of water at 90°C was added to the mixture of 2.0 parts of microcrystalline wax, 0.9 part of ethylene-vinyl acetate copolymer (Ultrcen 722; melt-flow rate: 400 g / 10 min.; made by Tosoh Corporation) and 2.9 parts of sorbitanmonooleate, followed by stirring and mixing thoroughly to obtain a water-in-oil type emulsion. Thereto added 3.8 parts (density : 0.25 g/cc) of glass microbaloons as hollow microspheres and stirred and mixed to obtain the water-in-oil type emulsion explosive of the present invention. The water-in-oil type emulsion explosive was molded into shape by extruder with dies of 8 mm in diameter, followed by cutting by knife in length of 10 mm to obtain the explosive of the present invention. The density of obtained explosive was 1.17.

With respect to the obtained explosive, the detonation velocity, agglomeration property and easiness in disagglomeration have been tested in the same way as Test example. The results are shown in Table 3. detonation velocity

(m/s) elapsed time forthwith after production dry hole 2865 watery hole 3005 6 months after dry hole 2789 watery hole 2990 1 year after dry hole 2978 watery hole 3129 solidification property elapsed time 6 months after slight partial agglomeration 1 year after slight partial agglomeration easiness in disagglomeration elapsed time 6 months after easy 1 year after easy

The water-in-oil type emulsion explosive of the present invention is hardly agglomerated or deformed; only a slight and partial agglomeration takes place even with a long- term storage such as 6 months or 1 year under a load, wherein the agglomeration can be easily come apart; it has excellent long-term stability and has excellent water resistance. Accordingly, if the explosive of the present invention is suitably molded, it can be easily charged into a blast hole with a pneumatic loader or so, and can also be used in the watery hole without losing its explosive performances. The residual gas compositions after blasting are also better compared with those of ANFO explosives'.