US3379588A - Manufacture of plastic high-power blasting explosive compositions and charges - Google Patents

Description

United States Patent ABSTRACT OF THE DISCLOSURE Plastic high-power blasting explosive compositions are provided comprising from Percent Nitrocellulose -20 Nitroglycerine 33-40 Crystalline high-explosive selected from the group consisting of cyclotrimethylentrinitramine, cyclotetramethylentetranitramine and pentaerythritol tetranitrate 40-60 Non-explosive substance To 5 The process for the manufacture of such materials is likewise provided. Such process comprises granulating under water and in the presence of a volatile water-immiscible solvent for nitrocellulose a mixture consisting of Percent Nitrocellulose 8-25 Nitroglycerine To 5 Inert plasticizer To 3 Stabilizer 0.5-2

Solid crystalline finely divided high-power explosive selected from the group consisting of cyclotrimethylentrinitramine, cyclotetramethylentetranitramine and pentaerythritol tetranitrate 65-92 removing the solvent and water from the granules, drying the granulated material, pouring the granulated material into a container, impregnating said material in the container with a liquid containing up to Percent Nitroglycerine 97 Inert plasticizer To 3 Stabilizer To 2.5 Accelerator To 3 and then curing the resulting mixture in the container at a temperature of about 5060 C. to obtain a consolidated plastic mass.

This application is a continuation-in-part of application Ser. No. 427,975 filed Jan. 25, 1965, now abandoned.

The present invention relates to an improved process for the manufacture of plastic high-power blasting explosive compositions and charges as well as to the products obtained thereby.

By the term high-power explosive, as employed in the instant specification and claims, are meant those explosives having a heat of explosion 21300 kcal. per kg., a detonation rate referred to the greatest technologically obtainable density 28000 m./sec. and a charging density 21.6 g./cu. cm.

Explosive chemical compounds having such characteristics can be either liquid or solid. However, those which are liquid (for example nitroglycen'ne) do not have, as such, any practical application.

Among the solid high-power explosive chemical com- "ice pounds which have been used in industrial practice are cyclotrimethylentrinitramine (RDX or Hexagen) melting point ZOO-201 C.; cyclotetramethylentetranitramine (HMX or Octogen)melting point 276277 C.; and pentaerythritol tetranitrate (PETN or Pentrite) melting point -141 C.

Modern military science has yet to deal with and solve definite problems concerning defense, which require the use of high-power explosives capable of withstanding severe stresses.

Solid high-power explosives cannot fully satisfy certain requirements of modern warfare for the following reasons.

The power of an explosive depends on its structure and in particular on the density of the oxygen-carrying groups (in the present case nitramine and nitroester groups) present in the molecule of the explosive.

From this it follows that high-power explosive chemical compounds, in the molecules of which the oxygencarrying groups are contained at such a concentration as to provide an amount of energy near to the maximum peculiar to complete combustion, are so sensitive to mechanical etfects as to discourage their use, particularly in cases in which the explosives are subjected to severe mechanical stresses.

These disadvantages are further accentuated by the aggregation state of the above considered high-power explosives, the solid state being the most suitable for absorbing large amounts of the energy generated by a direct impact resulting from a stress. This impact or by the impact energy, in solid explosives, turns in fact into heat energy, causing a temperature transient, which can attain levels on the order of hundreds of degrees and can start the decomposition and subsequent detonation of the explosive. A factor of remarkable importance which can contribute to the formation of decomposition spots is the heat developed as a result of the sliding friction between the crystals when the explosive is subjected to dynamic stresses.

From the practical viewpoint, the high-power solid explosives, owing to their aggregation state, can only be charged into ammunitions by means of a press with the manifold complications and limitations derived therefrom.

On the other hand, the use of fluxes, even if selected from the best and the most successful ones, while noticeably simplifying the charging operation, have not so far been used without affecting the power of the resulting explosive.

The object of this invention is to provide a process for converting into plastic form a crystalline high-explosive compound, sensitive to detonation by shock or friction, selected from the group consisting of the three abovementioned solid high-explosive compounds, namely RDX, HMX and PETN.

Another object is to provide a process for making plastic high-power blasting explosive compositions and charges which contain substantially only explosive substances, the proportion therein of inert agents being reduced to a minimum, and which explosives possess, however, a low sensitivity to initiation by friction or impact and are therefore capable of withstanding even severe mechanical stresses.

Still another object is to provide a process in which the charging of high-power explosives into ammunitions of any shape is made easy and safe.

Other objects and advantages will become apparent from from the following detailed description.

According to the present invention a process for the manufacture of high-power explosive compositions and charges of the character hereinbefore described is provided which comprises granulating under water and in the presence of a volatile water-immiscible solvent for nitrocellulose a mixture consisting of 8 to 25 percent of nitro cellulose, up to 5 percent of nitroglycerine, up to 3 percent of inert plasticizers, 0.5 to 2 percent of stabilizers, and 65 to 92 percent of a solid crystalline finely divided high-power explosive selected from the group consisting of cyclotrimethylentrinitramine, cyclotetramethylentetranitramine and pentaerythritol tetranitrate; pouring the resultant granulated material into a suitable container; impregnating the material in the container with a liquid containing up to 97 percent of nitroglycerine, up to 3 percent of an inert plasticizer, 1 to 2.5 percent of a stabilizer and up to 3 percent of an accelerator; and then curing the resulting mixture at a temperature of about 50 to 60 C. until the mixture has set into a consolidated plastic mass.

The granulation step is accomplished in a conventional granulating apparatus provided with a mechanical stirrer. For reasons of safety, the operation is performed under water. A volatile, water-immiscible solvent for nitrocellu lose is added to the water and preferably smaller amounts of additional ingredients are also added to the aqueous medium such as, for example, plasticizers for nitrocellulose e.g. nitroglycerine, the various phthalates, etc., stabilizers of nitroglycerine e.g. centralite, osmotic agents, sticking inhibitors and surface-active agents.

In this step, fibrous nitrocellulose, such as, for example, nitrated cotton, linters or wood pulp, is employed.

Suitable volatile water-immiscible solvents are well known and are for example, ethyl and isopropyl acetate, methyl ethyl ketone and the like or mixtures of these.

The resulting granules which hereinafter are also denominated as base granulated material or base granules consist essentially of a predominating proportion of the finely divided crystalline high-explosive compound embedded in a lesser proportion of gelatinized nitrocellulose as a matrix.

When granulation is terminated, the solvent is removed from the granules by distillation and the Water by filtration; the granules are then dried by conventional means at low temperatures (40-50 C.) until the total content of volatile substances does not exceed approximately 0.2 percent.

The base granulated material is then poured into a suitable container where it is impregnated with a liquid consisting essentially of nitroglycerine (up to 97 percent) and containing small amounts of additional ingredients, as for example, stabilizers for nitrate esters e.g. centralite, accelerators of the subsequent curing step, e.g. adipic dinitrile and preferably also a small proportion of another good plasticizer for nitrocellulose e.g. diethyl-phthalate and the like.

It is here to be pointed out that in this description the term impregnation means the method which consists in admitting the liquid through an opening in the container, previously filled with the base granulated material, until said liquid has reached the top of the container (the liquid and solid phase remaining distinct until gelation occurs in the subsequent curing step). Thus the terms impregnation and impregnating should be so construed in the instant specification and claims.

As above stated, the liquid employed for impregnating the base granules is substantially pure nitroglycerine. Other liquid explosive compounds such as for example dinitrotoluenes, ethyleneglycoldinitrate and the like are not suitable for use in this invention, because the resulting explosive products would not correspond to the requirements previously indicated for high-power explosives.

Subsequent to complete impregnation, the mixture in the container is cured at a temperature of about 5060 C. until it has set into a plastic consolidated mass.

Once the explosive has been made plastic as above described, it may be loaded into shells, bomb cases or other projectiles and warheads of any kind simply by introducing into such ammunition the plastic explosive, possi- 4 bly after shaping it into the desired form, or otherwise by setting it in the ammunition by the help of compression at a temperature of 50-60 C.

When the explosive is to be employed for other purposes, such as for example, for rupture-, cutting-, transmissionand destruction charges it can be shaped into the desired form by means of extrusion, rolling or moldlng.

Furthermore, in another aspect according to the present invention, the base granulated material can be poured directly into a projectile, warhead, etc. of any kind and shape, where it is impregnated and subsequently cured as above described so that a homogeneous consolidated plastic charge is obtained.

The compositions and charges prepared according to the invention, upon completion of the curing step, are perfectly compact and homogeneous and more or less plastic depending on their formulation; they remain plastic on storage. Their velocity of detonation is in any case at least 8000 meters per second.

The following examples are given to illustrate specific embodiments of the invention.

Base granulat- Imprcgnatin g Final comcd material liquid position Percent Percent Percent RDX 70 44. 38 N itroeellulose 22 13. 95 Nitroglycerlne.. 5 92. 5 37. 02 Diethylphthalate 2 3 2. 37 Centralite. 1 1v 5 1.18 Accelerator. 3 1. 10

P.E.T.N 25 15.18 RDX 50 30. 36 N itrocellulose 20 12. 14 Nitroglycerine- 2. 5 97 39. 62 Diethylphthalat 2. 0 2 2. 00 Centralitc 0. 5 1 0. 70

RDX 91 58. 24 Nitrocellulose. 8 5. 12 Nitroglyceiine 33. 12 Dicthylphthalate 1. 22 Centralite- 1. 40 Accelerator 0.

What is claimed is: 1. A process for the manufacture of a plastic highpower blasting explosive composition which comprises: A. granulating under water and in the presence of a volatile water-immiscible solvent for nitrocellulose a mixture consisting of Percent (1) Nitrocellulose 8-25 (2) Nitroglycerine T o 5 (3) Inert plasticizer To 3 Percent (1) Nitroglycerine T097 (2) Inert plasticizer T03 (3) Stabilizer 1-2.5 (4) Accelerator T03 and F. curing the resulting mixture in the container at a temperature of about 50-60 C. to obtain a consolidated plastic mass. 2. A process for the manufacture of a plastic highpower blasting explosive charge which comprises:

A. granulating under water and in the presence of a volatile water-immiscible solvent for nitrocellulose a mixture consisting of (5) Solid crystalline finely divided highpower explosive selected from the group consisting of cyclotrimethylentrinitramine, cyclotetramethylentetranitramine and pentaerythritoltetranitrate 65-92 Percent (1) Nitroglycerine To 97 (2) Inert plasticizer To 3 (3) Stabilizer 1-2.5 (4) Accelerator T0 3 and F. curing the resulting mixture in the ammunition at a temperature of about 50-60 C. to obtain a consolidated plastic charge.

References Cited UNITED STATES PATENTS Stettbacher 149-93 Stettbacher 149-93 Fassnacht et a1 149-95 X Wright et a1 149-93 X Kistiakowsky et a1. 149-92 Eckels 149-93 X Eckels 149-93 X De Wilde 149-93 X Fisher 149-92 Riedl 149-93 X CARL D. QUARFORTH, Primary Examiner. BENJAMIN R. PADGETT, Examiner. S. J. LECHERT, .TR., Assistant Examiner.