Classifications

• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B45/00—Compositions or products which are defined by structure or arrangement of component of product
• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B47/00—Compositions in which the components are separately stored until the moment of burning or explosion, e.g. "Sprengel"-type explosives; Suspensions of solid component in a normally non-explosive liquid phase, including a thickened aqueous phase
  • C06B47/14—Compositions in which the components are separately stored until the moment of burning or explosion, e.g. "Sprengel"-type explosives; Suspensions of solid component in a normally non-explosive liquid phase, including a thickened aqueous phase comprising a solid component and an aqueous phase
  • C06B47/145—Water in oil emulsion type explosives in which a carbonaceous fuel forms the continuous phase

Definitions

• the present invention relates to improved explosive composites comprised of oxidizing salts in intimate contact with molecular explosives.
• This intimate contact has been achieved by using the melt-in-fuel technology, the molecular explosive being part of the fuel phase.
• the explosive matters obtained by these means show very high densities and improved explosive features with respect to the molecular explosives considered.
• the explosive matters described in this invention can - substitute the current army melt cast ammunition like - composition B. They can also be used as boosters for - - industrial applications.
• amatols denotes a type of pourable explosive compounds comprised of ammohium nitrate (AN) and trinitrotoluene (TNT) of varying compositions. These composite explosives are prepared by dispersing AN in molten TNT with gentle agitation. The final product is castable at processing temperatures although presents a tendency for segregation of components (typical in TNT based multi-component melt-pour explosives). Different percentages of AN produce explosive composites of differentiated physical and explosive properties.
• AN ammohium nitrate
• TNT trinitrotoluene
• VOD velocities of detonation
• the U.S. Patent 4,545,829 describes methods for the preparation of W/O and O/W emulsions from TNT and AN and from TNT and ammonium perchlorate (AP). Two methods are shown in this patent. The first one requires heating of TNT to a temperature of 443 K. With regard to the second one, water is heated to 363 K and saturated with one of the salts mentioned above at this temperature. If O/W emulsions are formed, the solvent is evaporated off after emulsification has taken place. Although this preparation of amatols is undoubtedly novel, some processing and operational problems are apparent: (i) the impact sensitivity of TNT increases substantially with increasing temperature (see Picattini Arsenal).
• U.S. Patent 4,310,304 describes explosive formulations sensitive to the detonator prepared from an oxidizing phase comprised of inorganic salts and water and an organic phase comprised of mixtures of molecular explosives such as TNT, dinitrotoluene and dinitroxylene. These two phases were stabilized by using an appropriate emulsifier. Typical emulsification times of 5 minutes were required to achieve emulsification. Prior to the emulsion formation, microspheres were added to the water phase as a sensitizing agent. Densities in the range 1100-1150 kg.m ⁇ 3 were obtained.
• This high degree of intimacy can be obtained by using melt-in-fuel emulsion technology. Accordingly, the inorganic phase (eutectic mixture) would be the molten phase and the fuel phase would be comprised of molecular explosives.
• Inorganic oxidizing salts which are of utility in the present invention include AN, potassium nitrate (KN), sodium nitrate (SN), nitrates of alkaline earth elements, ammonium perchlorate (AP), perchlorates of alkaline and alkaline earth elements, organic nitrates such as hydrazine nitrate (HN), ethylenediamine dinitrate (EDDN), guanidine nitrate (GN), monoethanolamine nitrate (MEAN) and urea nitrate (UN).
• Eutectic mixtures of inorganic oxidizers showing melting temperatures ranging from 333 to 413 K will be preferred in order to ensure a safe handling of the raw materials during the emulsification process.
• melt-in-fuel emulsion obtained in the present invention is associated primarily with the crystallization kinetics of the oxidizing phase. Crystallization of this melt phase strongly depends upon droplet size, impurities of the components (heterogeneous nucleation), type of surfactant, presence or not of crystal modifiers and undercooling.
• this emulsion property is related to homogeneous nucleation (the lower the particle size, the slower the homogeneous nucleation) and is influenced by: (i) interfacial tension between both phases; (ii) overall viscosity (which is related to the shearing forces which break up the droplets during the emulsification process) and (iii) type of surfactant.
• interfacial tension between both phases (i) interfacial tension between both phases; (ii) overall viscosity (which is related to the shearing forces which break up the droplets during the emulsification process) and (iii) type of surfactant.
• undercooling appears to be of outmost importance. Thus, the higher the melting point the greater the undercooling (it should be recalled that the system is cooled to ambient temperature) and, consequently, the bigger the crystallization driving force.
• Molecular explosives which can be used as the fuel phase include TNT, trinitrochlorobenzene, 2,3-dinitroxylene, 2,5-dinitroxylene, 2,6-dinitroxylene, trinitroxylene, dinitrotoluenes and mixtures of them. These explosive fuel phases are used in the molten state. Other explosive fuels which must be used in solution include: hexogen and octogen in cyclopentanone solution. These two compounds are also slightly soluble in molten TNT.
• Other candidates to be explosive fuel phases comprise charge-transfer complexes (or ⁇ complexes) of TNT with aromatic nitro compounds such as 1,3,5-trinitrobenzene, 1-nitronaphtalene, 2-iodo-3-nitrotoluene, 2,4-dinitroanisole, 1,3-dinitrobenzene, tetryl and hexanitrostilbene.
• aromatic nitro compounds such as 1,3,5-trinitrobenzene, 1-nitronaphtalene, 2-iodo-3-nitrotoluene, 2,4-dinitroanisole, 1,3-dinitrobenzene, tetryl and hexanitrostilbene.
• the fuel phase must also include aromatic and aliphatic hydrocarbons which reduce the surface tension of the fuel phase.
• Adequate hydrocarbons are: mineral oil, parafinic and microcrystalline waxes, petroleum distillates, benzene, toluene, xylene, tetrahydronaphtalene, decahydronaphtalene, epoxy soya oil and mixtures thereof.
• HLB hydrophilic Lipophilic Balance
• Appropriate candidates include: isopropylamine docecylbenzene sulphonate, polyoxyethylene coconut amine, polyoxyethylene distearate, polyoxyethylene glycerol monostearate, polyoxyethylene monolaurate, sorbitan monoisostearate, sorbitan sesquioleate, tallow amine acetate, etoxylated tallow amine, ethyleneglycol oleate, glycerine monooleate, sorbitan monooleate, sorbitan monostesrate, sorbitan trioleate, polyoxyethylene sorbitan monooleate and polyoxyethylene sorbitan trioleate.
• this composite explosive could be prepared by two means: (i) homogenizing with a mixer at high - - revolutions ( 10000 r.p.m.) and (ii) injecting the fuel and oxidizing phases through a static mixer into which emulsification and subsequent droplet break up, as a consequence of shear forces, take place.
• the processing system used here comprises: 1. Feedstock units for the oxidizing combination phase and the fuel phase wherein melting of the components is carried out; 2. A degassing system; 3. A vacuum unit; 4.
• a static mixer. Emulsification of the composite explosives by means of this method requires the following steps: (i) melting of the oxidizing combination and the fuel phase at adequate temperatures in their corresponding feedstocks; (ii) introduction of both phases within degassing chambers where degassification is accomplished by means of a vacuum line; (iii) metering of the appropriate volumes of both phases and subsequent injection of them by means of a hydraulic system.
• the injection rate depends on the volumes which must be processed in order to ensure a homogeneous mixture - - between both phases. Mixing of these phases takes place in a static mixture as well as refinement of the emulsion thus formed.
• the pipes through which the molten phases circulate are kept at a prestablished temperature to avoid undesirable solidifications of any of both phases within the processor which could collapse the pipes and cause damage to the hydraulic system.
• the injection piston has been designed in order to prevent metal-metal frictions which could give rise to sparks and a possible subsequent detonation of the explosive compounds (due to adiabatic fracture of the explosives crystals) which are being processed. Accordingly, isolation of both phases from the pumping system has been achieved here by using a polytetrafluoroethylene (PTFE) joint Forseal-Foa which incorporates a stainless steel tension spring. Isolation is accomplished by lineal contact between the two edges of the joint, the spring being the static pressure element. The joint allows processing temperatures within the range 123 K to 493 K and shows good chemical resistance and no stick-slipping.
• PTFE polytetrafluoroethylene
• the uniaxial hydraulic piston of the processor of this invention is driven along the correct path by means of a glass fibre reinforced PTFE joint. Furthermore, this joint is characterized by high charge capacity, high abrasion resistance, optimum slipping qualities and absence of stick-slipping.
• Suitable additives include RDX, HMX, PETN, TATB, ONTA,...
• Table I includes explosive properties of composite explosive formulations which composition is disclosed in detail in the examples 1 to 6 described below. These properties have been calculated theoretically on the basis of the Chapman-Jouguet (C-J) detonation state. The Gurney velocities as well as the theoretical densities and oxygen balances are also included. The explosive properties of TNT alone have also been included for comparison. It should be noted that two have been the eutectics used for the preparation of these composite explosives: (i) a very high density one comprised of AN, KN and SN and (ii) a highly energetic one comprised of AN, KN and the explosive oxidizing salt EDDN. The properties evaluated in this way depend on the type of eutectic.
• formulations 1,2 and 3 show very high theoretical densities which yield very big values of VOD whereas the detonation temperature are much lower than the one calculated for TNT. Higher detonation pressures are also obtained for these formulations than for TNT alone. The Gurney velocity is also higher for these formulations than for TNT. With regard to the second eutectic, it yields composite explosives which have lower density than TNT. Despite this fact, VOD bigger than those found for TNT are obtained. The detonation temperature for these composite explosives prepared from the second - - eutectic is higher than the detonation temperature found for the formulations prepared from the first one due to the explosive character of the oxidizing salt EDDN.
• An eutectic mixture of AN (48.23 parts), KN (8.12 parts) and SN (13.65 parts) were heated above the melting point of the eutectic (403 K).
• the fuel phase comprised of TNT (16.2 parts), mineral oil (5.01 parts), tetrahydronaphtalene (5.8 parts) and the emulsifying system (3.3 parts) was prepared in a separate vessel at 363 K and subsequently added onto the molten eutectic mixture.
• the system was then agitated vigorously (10000 r.p.m.) during one minute. Emulsification of the ingredients took also place almost instantly.
• the compesite material thus prepared was also castable at 353 K.
• crystallization of the oxidizing salts and subsequent disrupture of the droplets took place after only one week from the preparation of the system.
• An eutectic mixture of AN (40.0 parts), KN (6.0 parts) and EDDN (34.0 parts) were heated above the melting point of the eutectic (376 K).
• the fuel phase comprised of TNT (8.04 parts), mineral oil (3.34 parts), tetrahydronaphtalene (5.3 parts) and the emulsifying system (3.3 parts) was prepared in a separate vessel at 363 K and subsequently added onto the molten eutectic mixture. The system was then agitated vigorously (10000 r.p.m.) during one minute. Emulsification of the ingredients took place almost instantly.
• the - viscosity of this system at 353 K was lower than the viscosity observed for examples 1, 2 and 3 at the same temperature.
• the composite material thus prepared was castable at 353 K. Solidification of the system when cooled to ambient temperature proceeded at a slower rate than for system 1, 2 and 3. The system showed a mean particle size of 1,9 ⁇ m. With regard to the stability of the emulsion, it was found that crystallization of the oxidizing salts and subsequent disrupture of the droplets was only apparent after two weeks from the preparation of the system. After four weeks, the crystallization was heavy and no droplets could be detected.
• An eutectic mixture of AN (35.0 parts), KN (5.25 parts) and EDDN (29.75 parts) were heated above the melting point of the eutectic (376 K).
• the fuel phase comprised of TNT (16.2 parts), mineral oil (5.01 parts), tetrahydronaphtalene (5.8 parts) and the emulsifying system (3.0 parts) was prepared in a separate vessel at 363 K and subsequently added onto the molten eutectic mixture. The system was than agitated vigorously (10000 r.p.m.) during one minute. Emulsification of the ingredients took place almost instantly.
• the viscosity of this system at 353 K was lower than the viscosity observed for examples 1,2 and 3 at the same temperature.
• the composite material thus prepared was castable at 353 K. Solidification of the system when cooled to ambient temperature proceeded at a slower rate than for system 1, 2 and 3. The system showed a mean particle size of 2.1 ⁇ m.
• the stability of the emulsion as for example 4, it was found that crystallization of the oxidizing salts and subsequent disrupture of the droplets was only apparent after two weeks from the preparation of the system. After four weeks, the crystallization was heavy and no droplets could be detected.
• An eutectic mixture of AN (30.0 parts), KN (4.5 parts) and EDDN (25.5 parts) were heated above the melting point of the eutectic (376 K).
• the fuel phase comprised of TNT (26.0 parts), microcrystalline was (6.67 parts), tetrahydronaphtalene (5.33 parts) and the emulsifying system (2.0 parts) was prepared in a separate vessel at 363 K and subsequently added onto the molten eutectic mixture. The system was then agitated vigorously (10000 r.p.m.) during one minute. Emulsification of the ingredients took place almost instantly.
• the sensitizer particles are suspended in the composite material by slow agitation under vacuum (vacuum mixing). By this mean, higher experimental densities can be attained. The high viscosity exhibited by these materials prevented segregation of the sensitizers and homogeneous mixtures were obtained. The minimum booster required to obtain detonation is also provided. Table II Compositions of the six possible formulations described in the text.

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Cited By (5)

Citations (9)

• 1990
  • 1990-12-31 EP EP90500130A patent/EP0493638A1/de not_active Withdrawn

Patent Citations (9)

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