JPH0210798B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a water-in-oil emulsion explosive composition (hereinafter abbreviated as W/O emulsion explosive composition).
The present invention relates to an explosive composition containing a novel emulsifier that forms a W/O emulsion,
This invention relates to a W/O emulsion explosive composition that has improved stability over time of detonation sensitivity and dead pressure resistance at small diameters (25 mm) and low temperatures. Regarding the W/O type emulsion explosive composition,
It has been researched for a long time, and the initial ones were because the morphology of the W/O emulsion was unstable (that is, the contact area between the dispersed phase and the continuous phase was relatively small), so explosive sensitizers such as nitroglycerin were used. Or non-explosive sensitizing agents such as monomethylamine nitrate (hereinafter abbreviated as sensitizing substances), or atomic number 13
Compounds of metals other than Groups 2 and 2 of the periodic table, explosive catalytic sensitizers such as water-soluble strontium compounds, or sensitizing oxidation agents such as perchlorates and chlorates of ammonium or alkali metals. Most of the bombs had improved detonation sensitivity at small diameters by adding agents (hereinafter abbreviated as auxiliary sensitive substances). However, W/O emulsion explosive compositions containing such sensitive substances or auxiliary sensitive substances may be susceptible to separation of the above-mentioned sensitive substances due to some factors during manufacturing or use, for example. There were potential dangers such as becoming extremely sensitive or the toxicity of the sensitive substances mentioned above. In this sense, W/O has improved detonation sensitivity in small caliber (detonator detonation is possible) without containing any of the above-mentioned sensitive substances or auxiliary sensitive substances.
Several type emulsion explosive compositions have also been disclosed. For example, according to US Pat. No. 4,110,134,
As an emulsifier, sorbitan fatty acid ester, glycerin fatty acid ester, polyoxyethylene sorbitol fatty acid ester, polyoxyethylene ether, polyoxyalkylene oleate, polyoxyalkylene laurate,
Contains phosphoric acid oleate, substituted oxazoline, and phosphoric acid ester, and contains glass microballoon as a bubble retaining agent. The diameter of the drug is approximately 1.25 inches (31.8 mm), and it reaches its peak in a No. 6 detonator 18 to 24 hours after manufacture. Completely explodes to a tentative specific gravity of 1.25 (drug temperature 21.1
℃～26.7℃). Further, according to US Pat. No. 4,149,917, emulsifiers include sorbitan fatty acid ester, glycerin fatty acid ester, polyoxyethylene sorbitol fatty acid ester, polyoxyethylene (4) lauryl ether, polyoxyethylene (2) ether,
Contains polyoxyethylene (2) stearyl ether, polyoxyalkylene oleate, polyoxyalkylene laurate, phosphoric oleate, substituted oxazoline, phosphoric ester, and mixtures thereof, and does not contain bubble-retaining substances. The tentative specific gravity was adjusted to 0.95 using microbubbles, and the diameter of the 1.25 inch (31.8 mm) bomb was completely detonated using a No. 6 detonator even after two months had passed since its manufacture (drug temperature was 21.1°C).
Even after 8 months have passed, a No. 8 detonator will cause a complete explosion (chemical temperature 21.1
°C). Furthermore, according to JP-A No. 55-75993, No. 55-75994, and No. 55-75995, a W/O emulsion explosive composition containing an imidazoline derivative, a mercaptan, and an oxyethylene oxypropylene block copolymer as an emulsifier is disclosed. Even after 30 temperature cycles (one cycle of 4 hours at 0°C and 7 hours at 40°C) without adding any sensitive substances or auxiliary sensitive substances, the product remained at No. 6 at -10°C to -20°C. Completely detonated with a detonator. However, the W/O emulsion explosive composition using the emulsifier described in the above-mentioned US patent specification and published patent application was prepared by the inventors at room temperature (10°C to 30°C).
°C) Temperature cycle test (60 °C) that reflects the passage of time well
After a cycle of 24 hours at -15℃ and 24 hours at -15℃, it was detonated with a No. 6 detonator at -5℃. 1 cycle is approximately room temperature aging 1
equivalent to months. ), it was 6 to 26 cycles (6 to 26 months), and in terms of stability over time, it was somewhat satisfactory considering the usage situation in Japan. However, since W/O emulsion explosives are inherently thermodynamically unstable, they are destroyed by many factors other than time, and the detonation sensitivity decreases with the degree of detonation, eventually leading to the detonator not detonating. up to. Among these, the most problematic phenomenon is the non-explosion phenomenon (generally called the "dead pressure phenomenon"), which is caused by the destruction of the emulsion form due to the action of bombardment waves and combustion gas from adjacent holes.
It is called. ). In that sense, the temperature cycle test mentioned above requires 6 to 26 cycles (6 to 26 months).
However, considering the stability of the W/O emulsion form and the non-explosive phenomenon (dead pressure phenomenon) mentioned above, it is still insufficient, and the detonation sensitivity over time at a smaller diameter (25 mm diameter) and lower temperature is still insufficient. A W/O emulsion with high stability and dead pressure resistance has been desired. As a result of intensive research over a long period of time while taking into account the above-mentioned problems, the present inventors have discovered a W/O obtained by using a new specific emulsifier.
It was found that the type emulsion explosive composition has performance superior to conventional known emulsifiers in terms of stability over time of detonation sensitivity at small diameters and low temperatures, and dead pressure resistance, and the present invention was completed. That is, the W/O emulsion explosive composition of the present invention comprises a dispersed phase of an oxidizing agent aqueous solution consisting of ammonium nitrate or ammonium nitrate and other inorganic oxide salts and water, and a continuous phase of a combustible substance consisting of fuel oil and/or waxes. A water-in-oil emulsion explosive composition comprising an emulsifier and micro hollow spheres or microbubbles, wherein the emulsifier is a maltitol fatty acid ester and/or a polyoxyalkylene maltitol fatty acid ester. It is a composition. The aqueous oxidizing agent solution of the W/O emulsion explosive composition of the present invention contains ammonium nitrate as a main component and contains other inorganic oxidizing acid salts as necessary. Here, the other inorganic oxide salts are, for example, nitrates of alkali metals or alkaline earth metals such as sodium nitrate and calcium nitrate. Also, alkali metal or alkaline earth metal perchlorates,
An auxiliary sensitizing substance such as chlorate or a sensitizing substance such as monomethylamine nitrate is not an essential component in terms of stability over time of detonation sensitivity and resistance to dead pressure, but may be blended. These inorganic oxidized salts are 1
Use as a seed or a mixture of two or more. The amount of ammonium nitrate is generally 46% to 94.69% of the total.
% (on a weight basis, the same applies hereinafter), and if necessary, other inorganic oxide salts may be contained in an amount of 40% or less of the total inorganic oxide salts containing ammonium nitrate. If the amount of ammonium nitrate is less than the lower limit, the oxygen balance (the relationship between excess and deficiency of oxygen between the oxidizing agent and the combustible agent) will be too poor (oxygen deficiency), resulting in poor explosiveness and aftergassing. If the upper limit is exceeded, the minimum dissolution temperature of ammonium nitrate in water becomes too high, resulting in poor productivity, and the explosive reactivity of ammonium nitrate becomes poor, resulting in poor detonation sensitivity. Regarding the other inorganic oxide salts mentioned above, by adding a small amount, the amount of oxygen supplied can be increased and the minimum dissolution temperature in water can be lowered, so explosiveness and manufacturability can be improved, but the amount exceeds 40%. This increases the amount of solid residue left after the explosion, resulting in lower power and disadvantages in terms of economy. Note that the amount of water used in the oxidizing agent aqueous solution is generally 5% to 25%. If it is less than 5%, the minimum melting temperature of ammonium nitrate or ammonium nitrate and other inorganic oxide salts becomes too high, resulting in poor productivity and poor detonation sensitivity due to poor explosive reactivity. If it exceeds 25%, the minimum melting temperature of ammonium nitrate or ammonium nitrate and other inorganic oxide salts will be lowered, which will improve productivity, but the amount of gas produced after the explosion, amount of heat, etc. will be reduced, resulting in poor detonation sensitivity.
Power is low. Fuel oils and/or wax fuel oils include hydrocarbons, such as paraffinic hydrocarbons, olefinic hydrocarbons, naphthenic hydrocarbons, aromatic hydrocarbons, saturated or unsaturated hydrocarbons, petroleum, refined mineral oils,
Lubricants, liquid paraffin, etc. and hydrocarbon derivatives,
For example, nitrohydrocarbons. Waxes include microcrystalline wax derived from petroleum, petrolatum, paraffin wax, etc., mineral waxes such as montan wax and ozokerite, animal waxes such as spermaceti wax, and insect waxes such as beeswax. It is. These fuel oils and waxes may be used alone or as a mixture of two or more. The amount of fuel oil and/or waxes is generally 0.1% to 10%. If the fuel oil and/or wax is less than 0.1%, the stability of the W/O emulsion explosive composition will be poor, and if it exceeds 10%, the oxygen balance will be too poor, resulting in poor explosiveness and aftergassing. Maltitol fatty acid ester and polyoxyalkylene maltitol fatty acid ester, which are new specific emulsifiers that can be used in the W/O emulsion explosive composition of the present invention, are, for example, maltitol or polyoxyalkylene maltitol and fatty acid. It can be produced by reaction with chloride or dehydration reaction of maltitol or polyoxyalkylene maltitol with fatty acids. Specifically, for example, maltitol or polyoxyalkylene maltitol is dissolved in a solvent, and pyridine is dissolved. It can be obtained by carrying out an esterification reaction by adding dropwise a fatty acid chloride under heating in the presence of a catalyst such as the following. The degree of substitution of the ester thus obtained is confirmed by acid value and saponification value as well as by thin layer chromatography. The compound thus obtained can be represented by the following general formula. Specifically, for example, maltitol lauric acid (mono, di, tri, tetra, penta, hexa) ester, maltitol oleic acid (mono, di, tri, tetra, penta, hexa)
Esters, maltitol isostearic acid (mono, di, tri, tetra, penta, hexa) esters, maltitol linoleic acid (mono, di, tri, tri,
Tetra, penta, hexa) ester, maltitol linolenic acid (mono, di, tri, tetra, penta, hexa) ester, maltitol erucic acid (mono, di, tri, tetra, penta, hexa) ester, etc. can. X=RCO− or H(R′O) _n − R=C _o H _2o+1 , C _o H _2o-1 , C _o H _2o-3 , C _o H _2o-5 (n
=9~24) R'=-CH ₂ CH ₂ - or

[Formula] m=0-20 These new specific emulsifiers are used alone or as a mixture of two or more. The amount of emulsifier added is generally 0.1% to 7%. Preferably 0.5% to 4
%. If these various emulsifiers are less than 0.1%, W/O
The type emulsion explosive composition has poor detonation sensitivity over time stability and dead pressure resistance at small diameters and low temperatures;
If it exceeds 7%, the oxygen balance becomes poor, resulting in poor explosiveness and aftergassing, which is also disadvantageous in terms of economy. Further, the W/O type emulsion explosive composition of the present invention has a temporary specific gravity of 0.80 to 1.35 by using a temporary specific gravity adjusting agent.
(preferably adjusted to 1.00 to 1.20). The temporary specific gravity adjusting agent is a micro hollow sphere or a micro bubble, and the micro hollow sphere is obtained from, for example, glass, alumina, shale, shirasu, silica sand, volcanic rock, sodium silicate, borax, nacre, obsidian, etc. Inorganic micro hollow spheres, carbonaceous micro hollow spheres obtained from pitch, coal, etc., synthetic resin micro hollow spheres obtained from phenolic resins, polyvinylidene chloride, epoxy resins, urea resins, etc.; The spheres may be used alone or as a mixture of two or more. The amount of micro hollow spheres is generally 0.1
%~10%. Microbubbles are, for example, microbubbles obtained by foaming a chemical foaming agent, or microbubbles obtained by mechanically blowing air or other gas during or after the formation of a W/O emulsion. Air bubbles, etc. Chemical blowing agents include, for example, inorganic chemical blowing agents such as alkali metal boron hydrides, those using a combination of sodium nitrite and urea, or N,N'-dinitrosopentamethylenetetramine, azodicarboxylic acid amide, azo These include organic chemical blowing agents such as bisisobutyronitrile. These chemical blowing agents may be used alone or as a mixture of two or more. The amount of chemical blowing agent is
Generally 0.01% to 2%. However, regarding the temporary specific gravity adjusting agent, the temporary specific gravity of the micro hollow spheres is less than 0.1%, the chemical blowing agent is less than 0.01%, or the W/O type emulsion explosive composition is
If the amount of air or other gas exceeds 1.35, the detonation sensitivity will be poor and even if the explosion occurs, the detonation velocity will be low. If the microhollow spheres exceed 10%, or if the chemical blowing agent exceeds 2%, or if the amount of air or other gas is such that the tentative specific gravity of the W/O emulsion explosive composition is less than 0.80. The detonation sensitivity is good, but the detonation speed is low, so the power is small. The method for producing the W/O emulsion explosive composition of the present invention is, for example, as follows. That is, an oxidizing agent aqueous solution is obtained by dissolving ammonium nitrate or a mixture of ammonium nitrate and other inorganic oxidizing acid salts in water at about 90°C to 95°C. On the other hand, the emulsifier defined in the present invention and fuel oil and/or waxes are heated at 90°C to 95°C.
A mixture (hereinafter abbreviated as combustible mixture) is obtained by melting and mixing at °C. Next, first put the combustible mixture in a heat-retainable container with a certain volume, and mix and stir for about 5 minutes at about 1600 rpm using a commonly used propeller blade stirrer while gradually adding the oxidizing agent aqueous solution. Obtain a W/O type emulsion at 90°C. Next, a W/O emulsion explosive composition is obtained by mixing micro hollow spheres or a chemical blowing agent into the W/O emulsion using a vertical mixer at about 30 rpm. In addition, when containing microbubbles made of gas such as air instead of microbubbles caused by microscopic hollow spheres or a chemical blowing agent, W/O emulsion can be mixed by stirring while blowing gas such as air into the W/O type emulsion. /O type emulsion explosive composition is obtained. Next, the W/O type emulsion explosive composition of the present invention will be specifically explained with reference to Examples and Comparative Examples.
Note that all parts and percentages in each example are based on weight. Example 1 A W/O type emulsion explosive composition having the formulation shown in Table 1 was manufactured as follows. First, 381.5 parts (6.30%) of ammonium nitrate and 22.85 parts (4.75%) of sodium nitrate were added to 55.25 parts (11.05%) of water and dissolved by heating to obtain an oxidizing agent aqueous solution at about 90°C. On the other hand, maltitol laurate monoester defined in the present invention
8.75 parts (1.75%) and microcrystalline wax (Wax Rex 602; manufactured by Mobil Oil)
The mixture with 17.05 parts (3.41%) was heated and melted to obtain a combustible mixture at about 90°C. Next, first put the combustible mixture in a heat-insulating container, then gradually add the oxidizing agent aqueous solution and mix and stir for 5 minutes at about 1,600 rpm using a propeller blade stirrer to bring the mixture to about 90°C. A W/O type emulsion was obtained. Next, 14.60 parts (2.92%) of glass micro hollow spheres (815/250; manufactured by 3M) with an average particle size of 75 μm were added to the W/O emulsion using a vertical mixer to approx.
A W/O emulsion explosive composition was obtained by mixing at 30 rpm. This W/O type emulsion explosive composition has a diameter of 25 mm, a length of approximately 170 mm, and a charge amount of 100 mm.
The tablets were molded to a size of 1.5 g, wrapped in viscose-processed paper, and subjected to various performance tests. Performance tests included (a) measurement of provisional specific gravity one day after production, and (b) repeated temperature cycles in which the sample cartridge was kept at 60℃ for 24 hours and then kept at -15℃ for 24 hours, with this as one cycle. After conducting a forced deterioration storage test, the number of temperature cycles that would result in a complete detonation when a detonation test was performed at -5℃ using a No. Detonation sensitivity temporal stability test estimated as the number of months of storage for complete detonation (estimated from the experimental confirmation that one temperature cycle described above corresponds to approximately one month of storage left at room temperature), (c) Temporary specific gravity measurement during the detonation test in (b) above, and (d) medicine packets wrapped in viscose-treated paper (drug amount).
100g) and 50g of dynamite are suspended at a certain distance, and 1 second after the 50g of dynamite is completely detonated, the test agent is detonated, and the maximum underwater pressure (Kg/ ^cm2 ) for complete detonation is set from the minimum distance for complete detonation. A converted dead pressure resistance test was conducted. The results were as shown in Table 1. The maltitol lauric acid monoester used was produced as follows. That is, to 1 mole of maltitol, 5 times the mole of pyridine was added as a catalyst, and further as a solvent,
100 times the mole of N,N-dimethylformamide was added and completely dissolved, and 1.5 times the mole of special grade lauric acid chloride was added dropwise thereto to start the esterification reaction. The reaction was carried out under stirring under anhydrous conditions.
The reaction was carried out at 50°C for 24 hours. After the reaction was completed, the solvent was removed under reduced pressure at 50°C, impurities were eluted with hexane, and the filtration residue was heated to 50°C.
It was dried under reduced pressure. Add water to this, stir well,
The pH was adjusted to 3 with phosphoric acid and filtered. The filtrate was taken into a separatory funnel, ethyl acetate was added thereto, and the mixture was thoroughly shaken.The ethyl acetate layer was taken and dried under reduced pressure using a rotary evaporator. Based on the acid value and saponification value of the obtained solid, the degree of ester substitution was 1.2. It was also confirmed by thin layer chromatography that the degree of substitution was mainly 1. Examples 2 to 11 A W/O emulsion explosive composition having a composition as shown in Table 1 contains maltitol oleate diester, maltitol isostearate triester, maltitol isostearate triester, maltitol isostearate triester, maltitol Toll linoleic acid tetraester, maltitol linolenic acid pentaester,
Maltitol erucate hexaester, polyoxyethylene (4) maltitol palmitate tetraester, polyoxyethylene (6) maltitol stearate pentaester, polyoxypropylene
(10) Produced according to Example 1 using the formulations of Examples 2 to 11 shown in Table 1, except that maltitol oleate hexaester and a mixture thereof were used. Sample cartridges were prepared from these W/O emulsion explosive compositions in the same manner as described in Example 1, and performance tests were conducted on the same items. The results were as shown in Table 1. The various emulsifiers mentioned above were obtained in a similar manner to the maltitol laurate monoester used in Example 1. The number in parentheses in the compound indicates the number of moles of ethylene oxide or propylene oxide added. This number of moles added was confirmed by gas chromatography. In the case of producing this compound, an esterification reaction is carried out using polyoxyethylene maltitol or polyoxypropylene maltitol instead of maltitol. Example 12 A W/O emulsion explosive composition having the composition shown in Table 1 was prepared in the same manner as in Example 1 except that N,N'-dinitrosopentamethylenetetramine was used in place of the glass micro hollow spheres. Produced according to Example 1. A sample cartridge was prepared from this W/O emulsion explosive composition in the same manner as described in Example 1, and this sample cartridge was heated in a constant temperature bath at approximately 50°C for 2 hours. Chemical blowing agent (N,
The same performance tests as in Example 1 were conducted on a product prepared by decomposing and foaming N'-dinitrosopentamethylenetetramine and adjusting its temporary specific gravity. Example 13 A W/O type emulsion explosive composition having the formulation shown in Table 1 was produced by the following method. That is, first, a W/O type emulsion was obtained according to Example 1. Next, while blowing air into the above-mentioned W/O type emulsion through a thin nozzle, mixing and stirring was performed at approximately 1600 rpm for 2 minutes using a propeller blade type stirrer to introduce microbubbles of air. An O-type emulsion explosive composition was obtained. Sample cartridges were prepared from this W/O emulsion explosive composition in the same manner as described in Example 1, and performance tests were conducted on the same items. The results were as shown in Table 1.

【table】

[Table] Comparative Examples 1 to 11 W/O type emulsion explosive compositions using known emulsifiers as shown in Table 2 were produced according to Example 1. A sample cartridge was prepared from this W/O emulsion explosive composition in the same manner as described in Example 1, and performance tests were conducted on the same items. The results were as shown in Table 2. Comparative Examples 12-13 Examples of W/O emulsion explosive compositions using known emulsifiers as shown in Table 2
Manufactured according to 12 and 13. A sample cartridge was prepared from this W/O emulsion explosive composition in the same manner as described in Example 1, and performance tests were conducted on the same items. The results were as shown in Table 2.

【table】

[Table] Examples of emulsifiers defined in the present invention include maltitol lauric acid monoester, maltitol oleic acid diester, maltitol isostearic acid triester, maltitol linoleic acid tetraester, maltitol linoleic acid pentaester,
Maltitol erucate hexaester, polyoxyethylene (4) maltitol palmitate tetraester, polyoxyethylene (6) maltitol stearate pentaester, polyoxypropylene
(10) In the case of W/O type emulsion explosive compositions containing maltitol oleate hexaester and mixtures thereof (Examples 1 to 9), the number of months of complete detonation storage at -5°C using a No. 6 detonator The period was 36 to 39 months, and the maximum pressure at complete explosion was 105Kg/cm ² to 124Kg/cm ² . On the other hand, in the case of W/O emulsion explosive compositions containing known emulsifiers (Comparative Examples 1 to 10), the storage time for complete detonation at -5°C using a No. 6 detonator is 6 months or more.
It took 26 months, and the maximum pressure at complete explosion was 40Kg/cm ² to 75Kg/cm ² . In addition, sodium nitrate and calcium nitrate are used as inorganic oxide salts other than ammonium nitrate, liquid paraffin is used as a combustible agent, silica micro hollow spheres (Silica Balloon NL; manufactured by Kushiro Coal Dry Distillation) are used as a bubble retaining agent, and polyoxyethylene (6) sorbitol is used as an emulsifier. W/O emulsion explosive composition containing 2.50% oleic acid tetraester (comparative example)
In the case of 11), the storage period for complete detonation at -5℃ using a No. 6 detonator is 28 months, and the maximum detonation pressure is 97
It was Kg/ ^cm2 . On the other hand, as an emulsifier defined in the present invention, maltitol oleate diester is used at 2.50%
The blended W/O emulsion explosive composition (Example 10) had a lifespan of 41 months and a maximum pressure of 192
It was Kg/ ^cm2 . Furthermore, maltitol oleate diester and maltitol linolenic acid pentaester are used as emulsifiers defined in the present invention, respectively.
The W/O emulsion explosive composition (Example 11) containing 0.8% polyoxyethykylene (6) maltitol stearate pentaester (Example 11) had a lifespan of 40 months and a maximum pressure of 170 kg/cm ² for complete detonation. It was hot. In addition, 0.2% of N,N'-dinitrosopentamethylenetetramine was added as a chemical foaming agent without adding a bubble retaining agent to adjust the temporary specific gravity, and polyoxyethylene (6) sorbitol oleate tetraester was added as an emulsifier. In the case of a W/O emulsion explosive composition (Comparative Example 12) containing 1.80% of
Using a No. 6 detonator, the storage time for complete detonation at -5℃ was 9 months, and the maximum detonation pressure was 38 Kg/cm ² , but instead of polyoxyethylene (6) sorbitol oleate tetraester, The W/O type emulsion explosive composition (Example 12) containing 1.80% of maltitol oleate diester defined in the invention had a life expectancy of 31 months and a maximum pressure at complete explosion of 79 kg/cm ² . In addition, a W/O emulsion explosive composition in which the tentative specific gravity was adjusted by mechanically introducing microbubbles without adding a bubble retaining agent, and 1.8% polyoxyethylene (6) sorbitol oleate tetraester was added as an emulsifier. In the case of the product (Comparative Example 13), the number of months it can be stored for complete detonation at -5℃ using a No. 6 detonator is 8 months.
The maximum pressure for complete explosion was 33 Kg/cm ² , but the W/O emulsion contained 1.8% maltitol oleate diester as an emulsifier defined in the present invention instead of polyoxyethylene (6) sorbitol oleate tetraester. The explosive composition (Example 13) had a lifespan of 32 months and a maximum pressure of 70 kg/cm ² at complete explosion. As described above based on each Example and each Comparative Example, a W/O emulsion explosive composition containing an emulsifier which is a maltitol fatty acid ester and/or a polyoxyalkylene maltitol fatty acid ester defined in the present invention. Compared to conventional W/O emulsion explosive compositions containing known emulsifiers, the explosive composition has significantly improved detonation sensitivity over time stability and dead pressure resistance at small diameters (25 mm diameter) and low temperatures. .

Claims (1)

[Scope of Claims] 1. A dispersed phase of an oxidizing agent aqueous solution consisting of ammonium nitrate or ammonium nitrate and other inorganic oxidizing acid salts and water, a continuous phase of a combustible substance consisting of fuel oil and/or waxes, an emulsifier, and microscopic hollow spheres or microscopic particles. A water-in-oil emulsion explosive composition comprising air bubbles, wherein the emulsifier is a maltitol fatty acid ester and/or a polyoxyalkylene maltitol fatty acid ester. 2. The water-in-oil emulsion explosive composition according to claim 1, wherein the proportion of the emulsifier is 0.1 to 7% by weight based on the total weight of the water-in-oil emulsion explosive composition.