GB2054551A - Nitroglycerine explosives - Google Patents

Abstract

A process for the production of nitroglycerine explosives comprises mixing nitroglycerine and/or nitroglycol with nitrocellulose, preferably at a temperature of less than 20 DEG C. Mixing is carried on until the surface of the mixture is 5-fold greater in relation to the starting surface and the gel begins to form as a semi-liquid compound which is blended with the remaining components of the explosive. The whole is mixed till a homogeneous mixture is obtained, and said mixture is formed into cartridges in paper or plastic casings.

Description

SPECIFICATION Process for the production of nitroglycerine explosives This invention relates to a process for the production of nitroglycerine explosives, which are both suitable for rock-crushing and safe towards coal dust and methane. The process of the invention is particularly useful for the production of explosives wherein the content of liquid explosive substances exceeds 20% by weight.

A known method of production of nitroglycerine explosives is carried out in the following way:- liquid explosives namely trinitroglycerine and/or nitroglycol, and nitrocellulose are blended cautiously, and then mixed, carefully. When the gel sets loose components of the explosive are added thereto and mixed. The mixed material is made into cartridges using paper or plastic casings.

A disadvantage of nitroglycerine explosives produced in the known way is the change in their shooting properties during storage. This change is very disadvantageous and results in a considerable reduction in both transmission of the detonation, and in the sensitivity of the material.

The reduction of sensitivity of the material to initiation is frequently so high that the material cannot be initiated with a detonator. This means that the material after having been stored for a long time is no longer suitable for use and must be destroyed.

Thus the nitroglycerine explosives produced in the known process show a maximum storage life of three months.

Another inconvenience of explosives produced in known processes is the exudation of nitroglycerine and/or nitroglycol during storage. The freshly prepared gel of nitroglycerine and/or nitroglycol and nitrocellulose is rigid. This rigidity of the gel is accounted for by the mechanical activity of incompletely dissolved nitrocellulose fibres contained in the gel. As the time goes by, as a result of the solvent action of nitroglycerine and/or nitroglycol, said fibres are softened, their rigidity is decreased, and also their capacity for absorbing nitroglycerine and/ or nitroglycol is reduced. if such a gel is submitted to pressure or to a temperature change then the particles of nitroglycerine and/or nitroglycol are isolated from the gel, which is defined as an exudation of nitroglycerine.

However, it has now been discovered that the solubility of air in nitroglycerine decreases rapidly at temperatures above 20"C. In order to take advantage of said effect, the operation of dissolving nitrocellulose in nitroglycerine, called gelling, should be conducted at temperatures of below 20"C, thus securing simultaneously in the course of gelling sufficient development of the surface of nitroglycerine, and a constant contact of so developed surface with air.

According to the present invention there is provided a process for the production of nitroglycerine explosives comprising the preparation of an explosive gelatine by mixing nitroglycerine and/or nitroglycol with nitrocellulose until the surface area of the nitroglycerine and/or nitroglycol in the course of mixing is increased to at least five times greater than the surface area of the nitroglycerine and/or nitrogiy- col prior to mixing and a semi-liquid compound is obtained, adding to the gelatine the remaining components of the explosive and mixing until a homogeneous mixture is obtained and thereafter making cartridges therefrom within a period of 8 hours using paper or plastic casings.

Preferably the preparation of the gelatine of nitroglycerine and/or nitroglycol is conducted at a temperature not exceeding 20"C until the semi-liquid compouned is obtained at which point the remaining components of the explosive are mixed in until a homogeneous mixture is obtained and that mixture is made into cartridges and seasoned at a temperature of at least 20"C for a period of at least 7 days.

Advantageously the mixing of nitroglycerine and/ or nitroglycol is carried out in a horizontal mixer having a semi-cylindrical bottom provided with agitator arms which rotate about the longitudinal axis of symmetry of said mixer so that in a first phase of rotation the components to be mixed are raised off the bottom and in a second phase of rotation the mixed components flow in a thin layer over the agitator arms onto the bottom of the mixer.

Instead of nitroglycerine, nitroglycol can be used, or preferably mixtures of nitroglycerine and nitroglycol. When nitroglycol alone is used the temperature below which the solubility of air in nitroglycol decreases rapidly is reduced to 1 SOC. For mixtures with the ratio of nitroglycerine to nitroglycol of 1:1 and more, said temperature is practically equal to 20"C.

Oxygen increases the chemical affinity of nitrocellulose to nitroglycerine and/or nitroglycol, assures that the gel has a higher osmotic pressure, and increases the ability of nitrocellulose to absorbing nitroglycerine and/or nitroglycol. Simultaneously, oxygen increases the solvent characteristics of nitroglycerine and/or nitroglycol with respect to nitrocellulose fibres which means that in the gelling process there is no forming of transitory rigid gel.

Most preferably the preliminarily gelled nitroglycerine and/or nitroglycol with nitrocellulose is blended with the remaining components of the explosive, mixed and made into cartridges at a temperature of below 20"C in paper of plastic casings. The cartridged explosive, preferably in shipping packings, is seasoned at a temperature of at least 20"C for a period of at least 7 days.

After mixing, the preliminarily gelled mixture of nitroglycerine and/or nitrog lycol with nitrocellulose covers with a thin layer the granulate component of the explosive. In the course of seasoning at a temperature of at least 20"C said mixture gels further on granulate components of the explosive, whereby simultaneously microscopic air bubbles are educed, which as a result of the high viscosity of the forming gel do not migrate to the surface of the layer, but form in said gel as a separate phase.

In a preferred embodiment the process according to the invention proceeds as follows: Nitroglycerine and/or nitroglycol, and nitrocellulose are blended cautiously and mixed carefully at a temperature not exceeding 20OC, so that the surface of the nitroglycerine and/or nitroglycol, contacting with air is at least five times largerthan the surface of the nitroglycerine and/or nitroglycol before starting the mixing. To the so prepared mixture, remaining components of the explosive are added and mixed until a homogeneous mixture is obtained and this material is formed into cartridges in paper or plastic casings, packed into packs and cartons, and seasoned at a temperature of at least 20"C for a period of at least 7 days.

The explosive preserves its shooting properties practically unchanged for a period of at least one and a half years.

In another embodiment the process according to the invention is carried out as follows: Nitroglycerine and/or nitroglycol, and nitrocellulose are blended cautiously and mixed carefully so that the surface of nitroglycerine and/or nitroglycol, contacting with air, is at least five times larger than the surface of this nitroglycerine and/or nitroglycol before starting the mixing. To the prepared mixture remaining components are added and mixed until a homogeneous mixture is obtained and this material isformed into cartridges in paper or plastic casings not laterthan 8 hours after mixing the explosive, and packed into packs or cartons.

Nitroglycerine and/or nitroglycol is a strong explosive sensitive to mechanical impulses and very dangerous during mixing. Preferably, the mixing of nitroglycerine and/or nitroglycol with nitrocellulose, securing at least fivefold development of the surface of liquid being mixed, is performed mechanically without participation of man in the following way: Nitrocellulose and nitroglycerine and/or nitrogly- col are introduced into a mixer having the form of an horizontal trough with a semi-cylindrically shaped bottom. Into the trough an agitator is introduced consisting of a horizontal shaftwhereon a series of flat equidistantly spaced discs is mounted. The longitudinal axis of the shaft is incidental with the longitudinal axis of symmetry of the trough bottom.

The agitator is driven mechanically, and it may be started from a safe distance. During a first phase of rotation of the shaft the discs lift the components to be mixed, and, in the next phase of the rotation the mixed components flow down over the discs in a thin layer, with its entire surface remaining in contact with air. The effectivity of mixing and development of the surface can be improved by employing flat rings connected with the shaft means offlat arms, the plane of the rings being nonperpendicular to the shaft axis.

The process according to the invention will now be described by way of the following Examples.

Example 7 23 kg of mixture of nitroglycerine and nitroglycol in a ratio of 1:1 by weight and 0.8 kg of nitrocellulose are introduced into a horizontal tank having a semi-cylindrical bottom. Then, an agitator consisting of an horizontal shaft whereon an inseparable series of flat discs is mounted, is introduced into the tank.

The distance of the discs from the bottom walls equals 2 cm and the angle oftheir inclination to the shaft amounted to 70 . The distances between the discs are equal to 5 cam. The agitator is rotated about its axis for 15 min. a speed of 15 r.p.m. The mixing is performed at a temperature of 15"C. From the dense liquid obtained, two samples, 100 g each, were collected. The first one was submitted to further gelation at a temperature of 15"C for 20 days. The second sample was submitted to further gelation also, for a period of 20 days, but at a temperature of 40"C. After said period both samples showed the form of an elastic gel.The gel obtained at the temperature of 1 5"C had a density of 1.478 g/cm3, and that obtained at the temperature of 40"C - a density of 1.220 g/cm3. A section of the surface of said gel showed pores barely visible under the microscope.

Thereafter, on removing the agitator, the thick liquid is carried over into a round pan, the remaining components of the explosive are added, namely 69.2 kg of ammonium nitrate, 6kg of dinitrotoluene, and 1 kg of sawdust, the charge is mixed using two vertical agitators for a period of 12 minutes. The material obtained having a soft plastic consistency is formed into cartridges in paper casings with a diameter of 32 mm in portions of 150 g each. The shooting properties of the material, on the fifth hour after ca rtridg- ing amount to: bulging in a lead block: 320 ml, detonation rate: 2800 m/s, detonation transmission: 3 cm, relative explosion force: 70%, initiation: detonator No. 2.The shooting properties after 15 days storage at 30"C and a relative humidity of 65% were: bulging in a lead block: 370 ml, detonation rate: 3400 m/s, detonation transmission: 6cm, relative explosion force: 80%, initiation from detonator No. 1, exudation - not recorded.

The above material - after having been stored for 15 months in a room at the temperature of 23"C and relative humidity of 80% showed the following shooting properties:- bulging in a lead block: 350 ml, detonation rate: 3200 m/s, detonation transmission: 9 cm, relative explosion force: 80%, initiation: detonator No. 1, exudation: not recorded,freezingand-defrosting test satisfactory.

Example 2 23 kg of mixture of nitroglycerine and nitroglycol in a ratio of 1:1 by weight, and 0.8kg of nitrocellulose are introduced into a horizontal tank having a semi-cylindrical bottom: then - into the tank an agitator is introduced, consisting of an horizontal shaft whereon an inseparable series of flat rings on flat arms is mounted. The distance of the rings from the bottom walls equals 2 cm, and the angle of their inclination to the shaft amounted to 70 . The distances between the rings are equal to 5 cm. The agitator is rotated about its axis for 15 min. art a speed of 15 r.p.m.

Thereafter - on removing the agitator, the thick liquid is carried over into a round pan and the remaining components of the explosive are added, namely: 69.2 kg of ammonium nitrate, kg of dinitrotoluene, and 1 kg of sawdust, the charge is mixed by means of two vertical agitators for a period of 12 minutes. The obtained material which has a soft plastic consistency is formed into cartridges in paper casings with a diameter of 32 mm in portions of 150 g each. The shooting properties of the material, on the third day after cartridging, amount to:- bulging in a lead block: 360 ml, detonation rate: 3200 m/s, detonation transmission: 7 cm, relative explosion force: 80%, initiation: detonator No 1, exudation: not recorded.

This material after being stored for 9 months in a room at the temperature of 23"C and relative humidity of 80% showed the following shooting properties:- bulging in a lead block: 355 ml, detonation rate : 3120 m/s, detonation transmission : 6 cm, relative explosion force: 78%, initiation: detonator No 1, exudation: not recorded. Freezing-anddefrosting test satisfactory.

Example 3 Explosive prepared as per Example 1 with the only difference that the composition is:- nitroglycerine and nitroglycol in proportion 1:1 by weight - 45 kg, nitrocellulose - 2 kg, ammonium nitrate - 49 kg, dinitrotoluene - 2 kg, sawdust - 2 kg. The shooting properties on the third day after cartridging are bulging in a lead block: 428 ml, detonation rate: 6200 m/s, detonation transmission: 11 cm, relative explosion force: 95%, initiation: detonator No 1, exudation: not recorded. The shooting properties after 20 months of storing in a room at a temperature of 25"C and relative humidity of 70% are as follows:- bulging in a lead block: 450 ml, detonation rate: 6000 m/s, detonation transmission: 8 cm, relative explosion force: 95%, initiation: detonator No 1, exudation: not recorded.

Freezing-and-defrosting test satisfactory.

Claims (5)

1. A process for the production of nitroglycerine explosives comprising the preparation of an explosive gelatine by mixing nitroglycerine and/or nitroglycol with nitrocellulose until the surface area of the nitroglycerine and/or nitroglycol in the course of mixing is increased to at least five times greater than the surface area of the nitroglycerine and/or nitroglycol prior to mixing and a semi-liquid compound is obtained, adding to the gelatine the remaining components of the explosive and mixing until a homogeneous mixture obtained, and thereafter making cartridges therefrom within a period of 8 hours using paper or plastic casings.

2. A process according to claim 1 wherein the preparation of the gelatine of nitroglycerine and/or nitroglycol is conducted at a temperature not exceeding 20"C until the semi-liquid compound is obtained at which point the remaining components of the explosive are mixed in until a homogeneous mixture is obtained and that mixture is made into cartridges and seasoned at a temperature of at least 20"C for a period of at least 7 days.

3. A process according to claim 1 or claim 2 wherein the mixing of nitroglycerine and/or nitroglycol is carried out in a horizontal mixer having a semi-cylindrical bottom provided with agitator arms which rotate about the longitudinal axis of symmetry of said mixer so that in a first phase of rotation the components to be mixed are raised off the bottom and in a second phase of rotation the mixed components flow in a thin layer over the agitator arms onto the bottom of the mixer.

4. A process for the production of nitroglycerine explosives according to any one of the Examples 1 3.

5. Nitroglycerine explosives whenever produced by a process according to any one of the preceeding claims.