Low temperature resistant emulsion explosive and method for preparing the same

Abstract

The application discloses low-temperature-resistant emulsion explosive and a preparation method thereof, and relates to the technical field of emulsion explosive. The emulsion explosive comprises the following raw materials in parts by weight: 500-1000 parts of ammonium nitrate, 50-100 parts of sodium nitrate, 5-15 parts of a surfactant, 30-50 parts of a composite wax, 10-20 parts of an emulsifier, 80-120 parts of water, 1-3 parts of modified nano silicon dioxide and 10-30 parts of a sensitizer. The surfactant is cocamide propyl betaine. The emulsifier is composed of polyisobutylene succinimide and xylitol oleate gemini emulsifier. Through the action of the emulsifier and the modified nano silicon dioxide, the structural maintaining capacity of the emulsion matrix under low-temperature conditions and the anti-water separation and anti-coalescence performance are remarkably improved. The added surfactant can also act on the modified nano silicon dioxide, so that the low-temperature resistance of the emulsion explosive is further improved.

Description

Technical Field

[0001] This invention relates to the field of emulsion explosives technology, and more particularly to low-temperature resistant emulsion explosives and their preparation methods. Background Technology

[0002] Emulsion explosives are highly dispersed colloids (belonging to the water-in-oil type) formed through emulsification technology, with fine droplets of an oxidizing agent aqueous solution as the dispersed phase and combustible hydrocarbon fuel as the continuous phase. They are currently the most widely used industrial explosives. Compared with ordinary powdered explosives (such as ammonium nitrate fuel oil explosives and expanded ammonium nitrate fuel explosives), they have unparalleled advantages, such as water resistance, complete explosive reaction, low toxic gas emissions, and no environmental pollution. In view of this, emulsion explosives have developed rapidly in recent years due to their excellent performance and economic efficiency. Especially in underground coal mines, open-pit mining, and engineering blasting, emulsion explosives have become the dominant industrial explosive. Major research institutions in China have also developed a variety of emulsion explosive products with their own unique characteristics. However, there is still a lack of emulsion explosives that can be used normally in environments below -30℃, which greatly affects winter construction in high-altitude and cold regions and special well drilling (freezing method). Therefore, it is necessary to develop low-temperature resistant emulsion explosives to meet these needs.

[0003] In open-pit mining, rock quarrying, and rock blasting for infrastructure construction in cold regions, developed mining countries such as the United States, Canada, and Russia commonly use powdered or gelatinous explosives with nitroglycerin as the sensitizer. The advantages of gelatinous nitroglycerin explosives are high power, good plasticity, strong water resistance, and good low-temperature performance; the disadvantages are relatively dangerous production and use processes, high mechanical sensitivity, high cost, and limited raw material availability, which restricts their application. Since the advent of emulsion explosives, their many superior properties have been recognized, and emulsion explosives have gradually replaced nitrate-based mixed explosives, with a wider variety available. However, the variety of anti-emulsion explosives remains limited and cannot meet the requirements of actual blasting (at -20℃ to -30℃).

[0004] Currently, in the frigid regions of Northeast and Northwest China, where winter temperatures range from -20℃ to -30℃ and during vertical shaft drilling in freezing conditions, small-diameter emulsion explosives are still commonly used. However, the explosive cartridges cannot be reliably detonated by detonators, affecting the progress of winter blasting projects. Furthermore, nitroglycerin-sensitized explosives are still used in some special blasting situations. However, nitroglycerin is a scarce and toxic raw material, relatively in short supply domestically, and expensive, making it unsuitable for my country's national conditions. Therefore, based on China's specific circumstances, it is crucial to develop a small-diameter, low-temperature resistant rock-type emulsion explosive with a cost close to that of ordinary No. 2 rock emulsion explosive, containing no high explosives or chlorates, usable in both normal and extremely low temperatures (-20℃ to 30℃), and reliably detonable by detonators. Summary of the Invention

[0005] Based on the technical problems existing in the background technology, the present invention proposes a low-temperature resistant emulsion explosive and its preparation method, which significantly improves the storage stability of emulsion explosives in low-temperature environments.

[0006] The present invention proposes a low-temperature resistant emulsion explosive, comprising the following raw materials in parts by weight: 500-1000 parts ammonium nitrate, 50-100 parts sodium nitrate, 5-15 parts surfactant, 30-50 parts composite wax, 10-20 parts emulsifier, 80-120 parts water, 1-3 parts modified nano silica, and 10-30 parts sensitizer.

[0007] Preferably, the modified nano-silica is prepared as follows: octadecyltrimethoxysilane, a silane coupling agent, and nano-silica are mixed and reacted in anhydrous ethanol to obtain modified nano-silica.

[0008] Preferably, the silane coupling agent is composed of γ-methacryloxypropyltrimethoxysilane and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane in a mass ratio of 2:1-4.

[0009] Preferably, the mass ratio of the octadecyltrimethoxysilane, the silane coupling agent, and the nano-silica is 20-40:10-20:100.

[0010] Preferably, the reaction is carried out at a temperature of 70-80°C for 12-36 hours.

[0011] Preferably, the surfactant is cocamidopropyl betaine.

[0012] Preferably, the emulsifier is composed of polyisobutylene succinimide and xylitol oleate gemini emulsifier in a mass ratio of 1-3:1.

[0013] Preferably, the sensitizer is one or more of hollow glass microspheres, sodium nitrite, perlite, and sodium borohydride.

[0014] This invention proposes a method for preparing a low-temperature resistant emulsion explosive, the low-temperature resistant emulsion explosive being described above, and the method steps are as follows:

[0015] S1: Mix the emulsifier and composite wax evenly to form the oil phase;

[0016] S2: Mix ammonium nitrate, sodium nitrate, surfactant and water evenly to form the aqueous phase;

[0017] S3: Mix and emulsify the oil phase and the water phase to obtain a latex matrix;

[0018] S4: Modified nano-silica and sensitizer are added to the latex matrix and stirred to obtain low-temperature resistant emulsion explosive.

[0019] Beneficial technical effects of the present invention:

[0020] This invention uses a compound of polyisobutylene succinimide and xylitol oleate gemini emulsifier to construct a more low-temperature resistant interfacial film structure by utilizing the division of labor and complementarity of the two at the latex matrix interface: polyisobutylene succinimide has strong hydrophobic anchoring ability and steric hindrance effect, which can form a stable interfacial adsorption framework in the composite wax-oil phase, thereby maintaining the integrity of the droplet boundary even when the system viscosity increases and the interfacial disturbance intensifies due to cooling; xylitol oleate gemini emulsifier, due to the paired distribution of amphiphilic groups and high interfacial coverage efficiency, can further reduce the oil-water interfacial tension and improve the compactness and elasticity of the interfacial film, making it less likely for droplets to aggregate and separate from the phase in a high-salt (ammonium nitrate / sodium nitrate) aqueous environment. Building upon this foundation, nano-silica modified with octadecyltrimethoxysilane and a specific silane coupling agent system is introduced. This allows the silica surface to possess both hydrophobic phase-compatible anchoring segments and polar sites capable of generating multi-point interactions, enabling "granular locking" on the interfacial film formed by the compound emulsifier. On one hand, a physical reinforcement layer is formed at the interface in a Pickering-like manner, suppressing interfacial embrittlement and droplet re-aggregation induced by wax phase crystallization at low temperatures. On the other hand, the methacryloyloxy and amino sites in the silane coupling agent can form hydrogen bonds / electrostatic associations with the polar groups of the emulsifier, creating an interlocking structure between the "emulsifier adsorption layer and the modified nano-silica particle layer." This elevates the low-temperature stabilization mechanism from a single molecular adsorption stabilization to a multi-scale composite stabilization of "molecular film + particle layer," significantly improving the latex matrix's structural retention and resistance to water separation and aggregation under low-temperature conditions.

[0021] This invention further introduces cocamidopropyl betaine as a surfactant, enabling it to form a synergistic stabilization mechanism with the aforementioned "compound emulsifier-modified nano silica" system. Cocamidopropyl betaine has an amphoteric structure, maintaining good interfacial activity even in the high ionic strength environment of the nitrate salt phase. It can preferentially improve the wetting and spreading of the water phase at the oil phase interface during emulsification, reducing the probability of initial large droplet and interfacial defect formation. Simultaneously, its zwitterionic head groups can adsorb / associate with the polar sites on the modified nano silica surface, playing a role in "softening charge-repairing defects-stabilizing micro-regions" on the interfacial layer of the compound emulsifier. During cooling, when wax phase crystallization or salting-out tends to cause interfacial stress concentration, betaine molecules can provide reversible ion association and hydration layer shielding at the interface, transforming the interfacial film from a "fragile single adsorption layer" into an "adaptive dynamic buffer layer." Through synergistic arrangement with the particle layer and emulsifier layer, it improves the continuity, toughness, and shear disturbance resistance of the interfacial film. This forms a ternary synergistic interface structure consisting of a "surfactant dynamic regulation layer - compound emulsifier skeleton layer - modified nano silica particle reinforcement layer", thereby further improving the low-temperature resistance of emulsion explosives. Detailed Implementation

[0022] The present invention will be further explained below with reference to specific embodiments.

[0023] The xylitol oleate gemini emulsifier of the present invention is prepared by succinic acid and xylitol oleate under the action of a catalyst, and the specific method is described in the prior patent application with publication number CN116375579A.

[0024] Example 1

[0025] Weigh out 15g of emulsifier and 40g of composite wax, and mix them evenly to prepare the oil phase material of the emulsion explosive. Separately weigh out 100g of deionized water, 80g of sodium nitrate, 755g of ammonium nitrate, and 10g of cocamidopropyl betaine, and stir to prepare the aqueous phase system of the emulsion explosive. The emulsifier is composed of polyisobutylene succinimide and xylitol oleate gemini emulsifier in a 2:1 mass ratio.

[0026] The prepared oil phase and water phase are heated to 100℃ respectively. After the oil phase is completely melted and the water phase is fully dissolved, they are transferred to an emulsification device and emulsified at a speed of 1000r / min to obtain a uniform and stable latex matrix.

[0027] Add 2g of modified nano-silica and 20g of hollow glass microspheres to the above latex matrix, adjust the stirring speed to 500r / min, and continue stirring for 2min to obtain the low-temperature resistant emulsion explosive.

[0028] The modified nano-silica is prepared as follows: 500 mL of anhydrous ethanol, 60 g of octadecyltrimethoxysilane, 30 g of silane coupling agent and 200 g of nano-silica are added sequentially to a 1000 mL three-necked flask. Magnetic stirring is turned on, the temperature is raised to 75 °C and maintained under reflux, and the reaction is carried out at a constant temperature for 24 h to obtain modified nano-silica. After cooling, it is sealed for later use.

[0029] The silane coupling agent is composed of γ-methacryloxypropyltrimethoxysilane and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane in a 1:1 mass ratio.

[0030] Example 2

[0031] Weigh out 10g of emulsifier and 30g of composite wax, and mix them evenly to prepare the oil phase material of the emulsion explosive. Separately weigh out 80g of deionized water, 50g of sodium nitrate, 500g of ammonium nitrate, and 5g of cocamidopropyl betaine, and stir to prepare the aqueous phase system of the emulsion explosive. The emulsifier is composed of polyisobutylene succinimide and xylitol oleate gemini emulsifier in a 1:1 mass ratio.

[0032] The prepared oil phase and water phase are heated to 100℃ respectively. After the oil phase is completely melted and the water phase is fully dissolved, they are transferred to an emulsification device and emulsified at a speed of 1000r / min to obtain a uniform and stable latex matrix.

[0033] Add 1g of modified nano-silica and 10g of hollow glass microspheres to the above latex matrix, adjust the stirring speed to 500r / min, and continue stirring for 2min to obtain the low-temperature resistant emulsion explosive.

[0034] The modified nano-silica is prepared as follows: 500 mL of anhydrous ethanol, 40 g of octadecyltrimethoxysilane, 20 g of silane coupling agent and 200 g of nano-silica are added sequentially to a 1000 mL three-necked flask. Magnetic stirring is turned on, the temperature is raised to 75 °C and maintained under reflux, and the reaction is carried out at a constant temperature for 24 h to obtain modified nano-silica. After cooling, it is sealed for later use.

[0035] The silane coupling agent is composed of γ-methacryloxypropyltrimethoxysilane and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane in a mass ratio of 2:1.

[0036] Example 3

[0037] Weigh out 20g of emulsifier and 50g of composite wax, and mix them evenly to prepare the oil phase material of the emulsion explosive. Separately weigh out 120g of deionized water, 100g of sodium nitrate, 1000g of ammonium nitrate, and 15g of cocamidopropyl betaine, and stir to prepare the aqueous phase system of the emulsion explosive. The emulsifier is composed of polyisobutylene succinimide and xylitol oleate gemini emulsifier in a mass ratio of 3:1.

[0038] The prepared oil phase and water phase are heated to 100℃ respectively. After the oil phase is completely melted and the water phase is fully dissolved, they are transferred to an emulsification device and emulsified at a speed of 1000r / min to obtain a uniform and stable latex matrix.

[0039] Add 3g of modified nano-silica and 30g of hollow glass microspheres to the above latex matrix, adjust the stirring speed to 500r / min, and continue stirring for 2min to obtain the low-temperature resistant emulsion explosive.

[0040] The modified nano-silica is prepared as follows: 500 mL of anhydrous ethanol, 80 g of octadecyltrimethoxysilane, 40 g of silane coupling agent and 200 g of nano-silica are added sequentially to a 1000 mL three-necked flask. Magnetic stirring is turned on, the temperature is raised to 75 °C and maintained under reflux, and the reaction is carried out at a constant temperature for 24 h to obtain modified nano-silica. After cooling, it is sealed for later use.

[0041] The silane coupling agent is composed of γ-methacryloxypropyltrimethoxysilane and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane in a mass ratio of 1:2.

[0042] Comparative Example 1

[0043] The silane coupling agent in this scheme is γ-methacryloxypropyltrimethoxysilane, and all other conditions are the same as in Example 1.

[0044] Comparative Example 2

[0045] The silane coupling agent in this scheme is N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and all other conditions are the same as in Example 1.

[0046] Comparative Example 3

[0047] The surfactant used in this scheme is sodium dodecyl sulfonate, and all other conditions are the same as in Example 1.

[0048] Comparative Example 4

[0049] The emulsifier in this scheme is polyisobutylene succinimide, and all other conditions are the same as in Example 1.

[0050] Comparative Example 5

[0051] The emulsifier in this scheme is xylitol oleate gemini emulsifier, and all other conditions are the same as in Example 1.

[0052] The low-temperature resistance of the emulsion explosives prepared in Example 1 and Comparative Examples 1-5 was determined, and the test results are shown in Table 1.

[0053] Using the latex matrices prepared in Example 1 and Comparative Examples 1-5 as the research objects, the latex matrices were stored at -30℃. The appearance of the latex matrices was analyzed, and the storage period and electrical conductivity of the latex matrices were recorded. The experimental results are shown in Table 1. Wherein:

[0054] Conductivity testing method: The dispersed phase of the latex matrix is ​​coated in the oil film. The leachate made from the latex matrix with intact internal structure has poor conductivity and the measured conductivity is low. However, when the oxidant aqueous solution breaks through the oil film, the highly polar ammonium nitrate is in the ionic state in the water, which enhances the conductivity and the conductivity will increase significantly.

[0055] After each vibration cycle, a certain amount of sample is taken to prepare a leachate. The conductivity meter is connected as required, and the measuring probe of the conductivity meter is first rinsed with the leachate to be tested. 50 mL of leachate is added to a beaker, and the measuring probe is completely immersed in the leachate (the measuring plate is completely submerged in the solution). After the reading stabilizes, the data of each measurement is read and recorded. Two measurements are taken for each group and the average is taken.

[0056] Table 1 Low-Temperature Resistance of Emulsion Explosives

[0057]

[0058] As can be seen from the experimental results of Implementation 1, the emulsion explosive prepared by the present invention has excellent low-temperature resistance, a storage period of up to 92 days, some whitening on the surface after 10 days, 10% whitening on the upper part after 40 days, 40% whitening after 70 days, and a non-obvious granular feel and 70% hardening after 92 days.

[0059] As can be seen from the experimental results of Example 1 and Comparative Examples 1 and 2, the present invention, which modifies nano-silica with γ-methacryloxypropyltrimethoxysilane and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, exhibits superior performance compared to single silane coupling agents. This is because the nano-silica modified by octadecyltrimethoxysilane and the specific silane coupling agent system of this application possesses both hydrophobic phase-compatible anchoring segments and polar sites capable of generating multi-point interactions on its surface, enabling the realization of "particle" properties on the interfacial film formed by the compound emulsifier. "Chemical locking": On the one hand, a physical reinforcement layer is formed at the interface in a Pickering-like manner to suppress interfacial embrittlement and droplet re-aggregation induced by wax phase crystallization at low temperatures; on the other hand, the methacryloyloxy and amino sites in the silane coupling agent can form hydrogen bonds / electrostatic associations with the polar groups of the emulsifier, so that the "emulsifier adsorption layer - modified nano silica particle layer" produces an interlocking structure, thereby upgrading the low-temperature stability mechanism from a single molecular adsorption stability to a multi-scale composite stability of "molecular film + particle layer", which significantly improves the latex matrix's ability to maintain structure and its resistance to water separation and aggregation under low-temperature conditions.

[0060] The experimental results of Example 1 and Comparative Example 3 show that the choice of surfactant in this invention further improves the low-temperature resistance of the emulsion explosive. This is because cocamidopropyl betaine has an amphoteric structure, which can maintain good interfacial activity in the high ionic strength environment of the nitrate salt phase. It can preferentially improve the wetting and spreading of the water phase at the oil phase interface during emulsification, reducing the probability of initial large droplet and interfacial defect formation. At the same time, its zwitterionic head group can adsorb / associate with the polar sites on the modified nano silica surface, and play a role in "softening charge-repairing defects-stabilizing micro-regions" on the interfacial layer of the compound emulsifier. During the cooling process, when the wax phase crystallization or salting-out tendency leads to interfacial stress concentration, betaine molecules can provide reversible ion association and hydration layer shielding at the interface, transforming the interfacial film from a "fragile single adsorption layer" to an "adaptive dynamic buffer layer". Through synergistic arrangement with the particle layer and emulsifier layer, it improves the continuity, toughness and shear disturbance resistance of the interfacial film. This forms a ternary synergistic interface structure consisting of a "surfactant dynamic regulation layer - compound emulsifier skeleton layer - modified nano-silica particle reinforcement layer," thereby further improving the low-temperature resistance of emulsion explosives. Conventional surfactants such as sodium dodecyl sulfonate cannot achieve the same effect.

[0061] The experimental results of Example 1 and Comparative Examples 4 and 5 show that the emulsifier of the present invention, composed of polyisobutylene succinimide and xylitol oleate gemini emulsifier, has a synergistic promoting effect on improving the low-temperature resistance of emulsion explosives. This is because polyisobutylene succinimide has strong hydrophobic anchoring ability and steric hindrance effect, which can form a stable interfacial adsorption framework in the composite wax-oil phase, thereby maintaining the integrity of the droplet boundary even when the system viscosity increases and the interfacial disturbance intensifies due to cooling; the xylitol oleate gemini emulsifier, due to the paired distribution of amphiphilic groups and high interfacial coverage efficiency, can further reduce the oil-water interfacial tension and improve the compactness and elasticity of the interfacial film, making it less likely for droplets to aggregate and separate from the phase in a high-salt (ammonium nitrate / sodium nitrate) aqueous environment.

[0062] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application. The scope of this application is defined by the appended claims and their equivalents, all of which should be included within the protection scope of this application.

Claims

1. A low-temperature resistant emulsion explosive, characterized in that, It contains the following raw materials by weight: 500-1000 parts ammonium nitrate, 50-100 parts sodium nitrate, 5-15 parts surfactant, 30-50 parts composite wax, 10-20 parts emulsifier, 80-120 parts water, 1-3 parts modified nano silica, and 10-30 parts sensitizer.

2. The low-temperature resistant emulsion explosive according to claim 1, characterized in that, The modified nano-silica is prepared as follows: octadecyltrimethoxysilane, a silane coupling agent, and nano-silica are mixed and reacted in anhydrous ethanol to obtain modified nano-silica.

3. The low-temperature resistant emulsion explosive according to claim 2, characterized in that, The silane coupling agent is composed of γ-methacryloxypropyltrimethoxysilane and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane in a mass ratio of 2:1-4.

4. The low-temperature resistant emulsion explosive according to claim 2, characterized in that, The mass ratio of the octadecyltrimethoxysilane, silane coupling agent, and nano-silica is 20-40:10-20:

100.

5. The low-temperature resistant emulsion explosive according to claim 2, characterized in that, The reaction is carried out at a temperature of 70-80℃ for 12-36 hours.

6. The low-temperature resistant emulsion explosive according to claim 1, characterized in that, The surfactant is cocamidopropyl betaine.

7. The low-temperature resistant emulsion explosive according to claim 1, characterized in that, The emulsifier is composed of polyisobutylene succinimide and xylitol oleate gemini emulsifier in a mass ratio of 1-3:

1.

8. The low-temperature resistant emulsion explosive according to claim 1, characterized in that, The sensitizer is one or more of hollow glass microspheres, sodium nitrite, perlite, and sodium borohydride.

9. A method for preparing a low-temperature resistant emulsion explosive, wherein the low-temperature resistant emulsion explosive is as described in any one of claims 1-8, characterized in that, The steps are as follows: S1: Mix the emulsifier and composite wax evenly to form the oil phase; S2: Mix ammonium nitrate, sodium nitrate, surfactant and water evenly to form the aqueous phase; S3: Mix and emulsify the oil phase and the water phase to obtain a latex matrix; S4: Modified nano-silica and sensitizer are added to the latex matrix and stirred to obtain low-temperature resistant emulsion explosive.

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