MXPA96002087A - Procedure for the production of an explosive or pirotecn device - Google Patents

Abstract

The present invention relates to a process for the preparation of an explosive or pyrotechnic device containing a dangerous solid explosive or pyrotechnic material in a housing, the process comprising the steps of: forming a dispersion of the ingredients of the explosive or pyrotechnic material, a sufficient quantity of the inert liquid to prevent ignition or detonation of the material by impact, friction, heating or electrostatic discharge, the formation of the dispersion in drops, the feeding of the drops in a cooling medium, to a temperature below the freezing point of the inert liquid, whereby the drops are frozen in solidified droplets, have a charge of the solidified droplets, in a housing for the pyrotechnic device, freeze-dried the charge of the solidified droplets in situ in the housing with which the dangerous material particles are produced, and optionally you, press, the particles inside the housing

Description

PROCEDURE FOR THE PRODUCTION OF AN EXPLOSIVE OR PYROTECHNIC DEVICE This invention relates to a process for the production of an explosive or pyrotechnic device that contains a dangerous explosive or pyrotechnic solid material within a housing. In this description a hazardous material is one that is capable of igniting or detonating under circumstances which may increase accidentally, when the material is being handled. The common procedure for the manufacture of explosive or pyrotechnic devices which contain encapsulated hazardous materials, for example lighters and detonators, develop various dangerous process steps and manufacturing conditions. Therefore the mixing together of the oxidants and fuels to form the pyrotechnic powders is normally a very dangerous operation, such as powders, and possibly, the ingredients are easily ignited by static electricity, impact, friction or heat. If the subsequent granulation of the mixed powder is required, this also develops additional hazardous operations and also requires the inclusion of additives, which are otherwise preferably omitted. The storage of hazardous material in voluble form, requires the facility of special deposits of expiosives, which are expensive and are frequently located in a remote place where the device is being manufactured. The transfer of the deposit to the place of manufacture requires taking precautions against dangerous operations. Usually, only small amounts of material can be transported and it needs to be in explosion-proof containers or stored in such small quantities that the production of the devices is interrupted frequently, thus increasing costs. In the production of the devices, safe quantities of the explosive or pyrotechnic material, it needs to be placed in the housings of the device. The dangerous operation requires a very special and expensive equipment. In most cases, the quantities that are required are also small which ensures the feeding of the material that can not be had and the performance of the device is adversely affected. The realization can also be affected by segregation of the ingredients, of the material, which can occur in a place where the material is being handled especially by loading the material in the housing. Furthermore, in each of the manipulations of material there is a danger of explosive dust.

The explosive or pyrotechnic material is usually pressed into the housing of the device, and this is a dangerous operation, which requires special equipment for the protection of the workers, and the manufacturing equipment for the effects of the accidental explosion. In a typical explosive or pyrotechnic device such as a detonator or a pyrotechnic, more than one powder is required, in addition to the number of charges, and the pressing operations, and consequently multiply the hazards and costs. The hazards are further aggravated by the contamination of dust from a final loading operation with which there is an extra danger to subsequent pressing and loading operations. It is an object of this invention to provide a safe method for the preparation of a device containing a charge in a container of an explosive or pyrotechnic material. According to this invention, a method for the preparation of an explosive or pyrotechnic device containing a hazardous solid explosive or pyrotechnic material in a housing comprises the steps of forming a dispersion of the ingredients of the explosive or pyrotechnic material in a sufficient quantity. of \? n of inert liquid to prevent ignition or detonation of the material by impact, friction, heat electrostatic discharge; the formation of the droplet dispersion; feeding the drops in a medium of cooling to a temperature below the freezing point of the inert liquid, whereby the drops are frozen in solidified droplets; driving a charge of the solidified droplets into a housing for the pyrotechnic device; freeze drying the charge of the solidified droplets in situ, in the housing to produce the particles of the hazardous material; and, optionally pressing, the particles within the housing. In the present description an inert liquid is a non-flammable liquid, which does not react with any of the ingredients of the explosive or pyrotechnic material and is effective to suppress the reaction of the material both in the liquid form and in the frozen form. The inert liquid may comprise a solvent for the men < s one of the reactive ingredients of the explosive or pyrotechnic material, in the case of dissolution and the subsequent freeze-drying of the solution of the reactive ingredients that produce this ingredient in a very fine microporous crystalline, which has an increased reaction efficiency . The greater amount of the preferred liquid comprises water and the water is effective especially for the pyrotechnic compositions, which contain one or more of the water-soluble components. The dispersion can be formed in a conventional manner by mixing the ingredients of the explosive or pyrotechnic material with the inert liquid, although it is necessary to obtain a preferred viscosity for the formation of the drops and / or to prevent the segregation of the ingredients , a thickening agent, can be added to the inert liquid. If other ingredients are desired, for example modifiers or fillers, they can optionally be included in the dispersion. The dispersion can be conveniently formed into droplets by spraying through one or more orifices or by projecting the periphery of a disk or a rotating basket. The preferred droplet diameters - are in the range of 50-500 microns and more preferably in 75-200 microns. The cooling medium can be liquid, for example liquid air or liquid nitrogen, although in general a gaseous medium is preferred in order to avoid the distortion of the shape of the drops.

Suitable cold gases comprise air, nitrogen, carbon dioxide, argon, helium, and mixtures of two or more thereof. The temperature of the cooling medium can conveniently be in the range of -40 to -195 ° C, and preferably -80 ° C. The cooling medium can advantageously be recycled through cooling devices or cooled by a recycled refrigerated fluid in a known manner. After being passed through a cooling medium, the solidified droplets are substantially spherical, each droplet containing the ingredients of the explosive or pyrotechnic composition in the correct proportions is uniformly dispersed in a matrix of a frozen inert liquid (which is ice when the inert liquid is water). Mediate the adjustment of droplet formation conditions, for example the concentration of the material in the inert liquid, the diameter of the spray orifice, the spray pressure, and the temperature of the cooling medium, the distribution of the droplet size solidified and the material action can be regulated to ensure that the material reacts efficiently and that the flow characteristics of the material are such that they can be simply managed and safety in the operations of the subsequent procedure. The collected solidified droplets can, if desired, be kept indefinitely frozen in refrigerated storage until it is required for the additional procedure, since segregation of the products can not occur. When it is required that a charge of the solidified droplets be placed in a housing, for example a metal housing such as an ignition vessel or a detonation tube, the charge is pressed if necessary. This loading operation is free from the danger that is present in the charge of the dry particulate pyrotechnic compositions. According to this, the loading operation does not require special equipment, there is no risk that the workers of the procedure, and the amount of the material in the cargo feeding containers are not restricted. The amounts of the additional powder components, either of the same or of the different composition which may be required in certain devices that can be charged in a housing using the same procedure as described above. The process of the invention is especially advantageous for the preparation of the devices containing a very small amount, the pyrotechnic material according to the ingredients of the pyrotechnic material can be dispersed in a large comparative amount of the inert liquid so that the solidified drops required can be Be large enough for safe measurement and handling. In the freeze-drying step, the drops solidified in the container are subjected to a vacuum chamber at the temperature and pressure conditions, in which the vapor of the inert liquid is removed from the drops solidified by sublimation, without founds the liquid in the drops. The solidified droplets are preferably treated in a vacuum chamber maintained at a pressure below the triple point of the inert liquid, which for water is 6.11 millibar, the pressure is preferably maintained at 0.1 to 2 millibar, and they are preferably heated to supply the heat of sublimation of the inert liquid, and to increase the vapor pressure without melting any of the constituents of the drops. The vapor can be conveniently condensed in contact with a cold surface, leaving the dry particles frozen from the pyrotechnic material. The particles in the container can advantageously be pressed under vacuum, this operation is conveniently carried out in the same chamber without vacuum, in which, the solidified drops in the container are dried by freezing, without the removal of the dry particles in the chamber container. The pressure under vacuum conditions facilitates compression of the material and eliminates the possibility of adiabatic heating. The hazardous material remains completely safe from accidental ignition or explosion until after the freeze drying stage. Consequently, only the operations of the procedure subsequent to this stage, such as pressing the dry material by freezing in the housing, need to be carried out with specialized equipment designed to avoid accidental explosion, which can cause damage to the operators and damage the process machinery. The devices, which can be advantageously manufactured by this invention, include detonators, pyrotechnic devices, lighters, pyromechanisms, and protruding devices (gas generation), which may contain for example hazardous ingredients comprising the lead azide, sodium azide, mercury fulminate, pentaerythritol tetranitrate (PETN), lead mono- and di-nitroresorcinate, lead stifnate, barium stifnate, potassium dinitrobenzofuroxan (DNBF), cyclotrimethylene trinitra (RDX), and cycotetramethylene tetranitramine (HMX), and mixtures of two or more thereof; a dangerous composition comprising such hazardous ingredients; or a hazardous composition comprising generally safe materials, which become hazardous, when mixed together, for example, black powder, the boron / potassium nitrate mixture, a mixture of potassium perchlorate / perchlorate, or a mixture of -zirconium / potassium perchlorate. The dangerous material freeze-dried in the -location of the device can be ignited in a conventional manner appropriate, for example, by the flame of the ignition material or an electric bridge wire or by a shock wave, a shock tube or a detonation fuse head. The invention is especially advantageous for the preparation of devices containing the primary explosive compositions, for example, lead azide, in a very fine sensitive form, which can not be safe to be made and handled by conventional methods. The invention is further illustrated by the following specific Examples wherein all parts and percentages are given by weight. Example 1 The manufacture of a lighter with a single pyro-technical load. The lead stifnate is mixed with water to form a suspension of 50% lead stifnate and 50% water. The suspension is passed through a nozzle to form the droplets with a size range of 100 to 400 microns. These drops are frozen by directing the spray on the liquid nitrogen in a Dewar container. The solidified droplets are separated from the liquid nitrogen using a sieve, and stored in a freezer that is maintained at -40 ° C. 160 mg of 1 are directly weighed; s solidified droplets in a copper vessel lined with tin, with a diameter of 6.73 mm, length of 9.50 mm. , and with a wall thickness of 0.15 mm. The solidified drops fill the container to a depth of 5.4 mm. The container is then placed under vacuum in a commercial freeze dryer (Type Ed ards), for one hour, then for one hour at 70 ° C. The dry powder fills the container to a depth of - 2.2 mm. Then a sealed glass-to-metal heater already placed in the vacuum chamber and having a thin bridge wire (initiator), is connected between two bolts of the metal conductor which is pressed into the filled container in the chamber without vacuum to compress the dry powder and place the bridge-wire in contact with the lead stifnate, this operation is carried out under safety conditions in which precautions are taken to protect operations and equipment. The pressed powder fills the container to a depth of 0.9 mm. During pressure operations, the metal container tightens uniformly in the heater to complete the fabrication of a ignition. In the passage of an electric current of two amperes through the bridge wire, the lead stifnate is ignited. The container that burns opens in 752 raicoseconds. Example 2 An ignition device is prepared as described in Example 1, except that barium stifnate is used in place of lead stifnate. A current of two amperes is passed through the bridge wire, again the vessel burns in approximately 750 microseconds. Example 3 The manufacture of a conveyor device (actuator). An ignition device is prepared as in Example 1, which is inserted into one end of a metal cylinder and held firmly in place by the pressure of the cylinder on the end of the container with the ignition device containing the heater, the driver's bolts connect to the loads that extend outside the cylinder. A piston which is a sliding fit on the cylinder and which is attached to a piston rod of much smaller diameter, is inserted at the other end of the cylinder against the end of the ignition vessel containing the charge of the lead stifnate, the piston rod extending from the cylinder end. The end of the cylinder is tightened around the piston rod in order to retain the piston in the cylinder. When an electric current of 2 amperes is passed through the ignition device, the piston and the piston rod are pushed forward with a similar impulse for the conventional explosion, which the transport devices have. The driven piston rod can be adapted to perform the usual mechanical functions of the mechanical actuators, for example the interruption and cutting operations. Example 4 An ignition device is prepared as mentioned in Example 4, except that the container is in the form of a cylindrical bellows having a wall thickness of 0.25 mm. In the passage of a current of 2 amperes through the bridge wire, the bellows expand to drive the end of the bellows axially with an impulse layers to perform the usual functions of the actuators that work explosively. Example 5 The manufacture of an ignition device with two filling materials. Two pyrotechnic powders in the form of solidified droplets are prepared as mentioned in Example 1. The first powder containing 60% potassium nitrate / boron in mixture with oxygen balance, in 40% water, and the second powder that It contains 40% barium stifnate in 60 of water. A tin coated copper vessel as described in Example 1 is first filled with 133 milligrams of the first powder. Through the smooth distribution in the powder container, which is left at a surface level and the container is filled to a depth of 4.6 mm. Then 62 milligrams of the second powder is added to the container. Through the smooth distribution in the powder container, which is left at a surface level, the total depth of the powder is 7.0 mm. The powders are then dried by freezing in the container as mentioned in Example 1. After drying, the depth of the powder is 5.3 mm. Boron dust / potassium nitrate that >; retains its physical form during the drying process, while barium stifnate collapses. A sealed glass-to-metal heater is pressed into powder, as described in Example 1. The depth of the compressed powder is 1.5 mm. An electric current of 2 amps is passed through the wire bridge, the powder ignites and the container burns open in 75 microseconds. Example 6 Manufacture of a semi-conductor bridge ignition device. A frozen powder consisting of 50% barium stifnate and 50% water is prepared by the procedure described in Example 1. The average size of the particles of barium stifnate is 5 microns. 150 milligrams of frozen powder is loaded into a container as mentioned in Example 1. The container is pressed, so that the surface of the powder is leveled, the depth of the powder is approximately 5.5 mm. A sealed glass-to-metal heater, which has a semi-conductor bridge, is connected between two metal bolts, pressed into the filled container and depressed as mentioned in Example 1, to complete the device of ignition. The pressurized powder fills the container to a depth of approximately 1.0 mm. An electric current of 0.75 amperes is passed through the semi-conductor bridge, the ignition device container burns open in 800 microseconds. Example 7 The manufacture of an electric detonator. A frozen powder consisting of 60% of the lead azide, and 40% of water, is prepared by the procedure described in Example 1. 1.33 milligrams of the frozen powder is loaded in an aluminum detonator with a diameter of 7.0 mra. in the form of a tube, pre-cooled to 20 ° C. , and that has 500 milligrams of PETN, already pressed in the base. The depth of the lead azide powder frozen in the container is 3.5 mm. The lead azide powder is freeze-dried as described in Example 1, after which the depth of the remaining dry lead azide is about 2.0 mm. The dry lead azide is then pressed under protective conditions, by a rod with a flat end, of a diameter slightly smaller than that of the tube. The depth of the pressed lead azide (primary charge) is approximately 0.5 mm. This is then coupled into a conventional electric fuse head detonator, which upon ignition, is found to be equivalent to conventional electric detonators.

Example 8 Detonator initiating a shock tube. An aluminum detonator tube is charged with a PETN base charge, and a pressed primary charge, of the lead azide as mentioned in Example 7. An open end of a shock transmission tube (Nonel - Registered Trade Mark) It is inserted into the open end of the detonator tube. On ignition the firing tube of the detonator ignited and performed as a conventional detonator. Example 9 The manufacture of a propellant device / gas generator. A suspension of sulfur and carbon in a solution of potassium nitrate is made by dissolving potassium nitrate in water at 50 ° C. , and the addition of sulfur and carbon to the solution. The water content is 40% of the suspension. The suspension is formed into solidified droplets by the procedure as described in Example 1. A weight of 1.67 grams of the solidified droplets is weighed in a thick walled tube with a diameter of 12 mm. , a length of 25 mm., which is closed at one end by an ignition disk. Droplets fill the tube to a depth of 18 mm. The tube is then placed in a commercial freeze dryer, and left under vacuum at 30 ° C, for two hours, and then at 70 ° C, for two hours. There is no change to the physical dimensions of the powder you have during drying. An electric fuse head ignition device is inserted into the open end of the tube, so that the head of the fuse protruding slightly in the dust that is lost, the driver being driven from the ignition device is stopped through the open end of the tube. The tube is compressed around the load of the driver. The assembled device is placed inside a closed 62 liter pressure vessel. An electric current of an amper is passed through the head of the fuse, after a delay of approximately one millisecond, the pressure in the chamber is observed to rise to approximately 5000 Pascais, over the next 3 milliseconds. When the container is opened, it is found that all the powder in the tube has burned.

Claims (10)

1. CLAIMS 1.- A process for the preparation of an explosive or pyrotechnic device containing a dangerous solid or explosive pyrotechnic material in a housing, a process comprising the steps of: forming a dispersion of the ingredients of the explosive or pyrotechnic material, in an amount enough of the inert liquid to prevent ignition or detonation of the material by impact, friction, heating or electrostatic discharge; the formation of the droplet dispersion; feeding the droplets in a cooling medium, at a temperature below the freezing point of the inert liquid, whereby the drops are frozen in solidified droplets; have a charge of the solidified droplets, in a housing, for the pyrotechnic device; drying by freezing the charge of the solidified droplets in situ in the housing whereby the particles of the hazardous material are produced; and, optionally, pressing, the particles within the housing.
2. 2. A process according to clause 1, characterized in that the inert liquid comprises a solvent for at least one reactive ingredient of the explosive or pyrotechnic material and, optionally, comprises a thickening agent.
3. 3. A method according to clause 1, characterized in that the cooling medium comprises a liquid, for example liquid air or liquid nitrogen.
4. 4. A process according to any of clauses 1 to 3, characterized in that the cooling medium comprises a gas, for example, air, nitrogen, carbon dioxide, argon, helium or a mixture of two or more thereof.
5. 5. A method according to any of clauses 1 to 4, characterized in that the temperature of the cooling medium is in the range of -40 to -195 ° C.
6. 6. A method according to any of clauses 5, characterized in that the step of freeze drying comprises subjecting the solidified drops in the container to a vacuum chamber at temperature and pressure conditions in which the vapor of the inert liquid it is eliminated from the solidified drops, by sublimation, without the fusion of the liquid in the drops, or disturbance of the physical integrity of the same.
7. 7. A method according to clause 6, characterized in that the solidified droplets are maintained in the vacuum chamber at a pressure below the triple point of the inert liquid.
8. 8. - A method according to clause 6 or the clause 7, characterized in that the drops solidified in the vacuum chamber are heated by supplying the heat of sublimation of the inert liquid and the increase of the vapor pressure without melting any of the constituents of the liquid. the drops .
9. 9. A method according to any of clauses 1 to 7, characterized in that the soidified drops are placed in a metal housing, for example an ignition container or a container of a detonator, and freeze drying, dried particles by freezing in the vessel optionally they are pressed into the housing under vacuum conditions.
10. 10. A procedure according to clause 1, characterized in that the dangerous material comprises lead azide, sodium azide, mercury fulminate, PETN, lead mono-nitroresorcinate, lead dinitroresorcinate, lead stifnate, barium stifnate, dinitrofuroxan of potassium, trinitramine of cyclotrimethylene, or tetranitramine of cyclotetramethylene, a hazardous composition, which comprises any of one or more of the hazardous materials, or a hazardous composition comprising safety materials, the limes become dangerous when mixed together, with, for example, black powder, a mixture of potassium nitrate / boron, a mixture of potassium perchlorate / boron, a mixture of potassium perchlorate / titanium, or a mixture of potassium perchlorate / zirconium. EXTRACT OF THE INVENTION The invention provides an improved method for the production of an explosive or pyrotechnic device., which contains a hazardous solid material in a container, where the material is dispersed in an inert liquid, the dispersion is formed into drops and the drops are solidified, in a cooling medium. The solidified droplets are charged to a housing and drying by freezing in situ, in the housing produces the dry particles of the hazardous material, whereby it can optionally be pressed into the housing, advantageously under vacuum. Only operations (if any), subsequent to freeze-drying, require special precautions to avoid damage to personnel or equipment. The invention is advantageous for the preparation of detonators, igniters, and other devices containing hazardous materials, for example lead azide, lead stifnate, pentaerythritol tetranitrate, and potassium nitrate mixtures. boron.