US2334149A - Explosive - Google Patents

Description

oxygen carrier, such as Patented Nov. 9, W43

EHLOSIVE No Drawing.

Bronxville, N. Y.,

assignor to Application August 17, 1939, Serial No. 290,630. In Canada February 18, 1938 11 Claims.

The present invention relates to explosive compositions of the type in which an absorbent carrier is used.

The so-called dynamites, permissible explosives and the like, usually consist of a liquid explosive component such as nitro-glycerine, nitro-glycols, or other nitrated bodies, together with an explosive salt such as ammonium nitrate and/or an sodium nitrate, sodium and potassium chlorate and sodium and potassium perchlorate, together with an absorbent, In some instances, absorbents of the diatomaceous earth type are used. In these cases, the absorbent is entirely inert, that is, it contributes nothing toward the eventual explosion. For this reason, a carbonaceous -combustible material is preferred as the absorbent. absorbents are usually of vegetable origin, such as plant tissues and such substances as ground cork, bagasse pith, balsa wood, wood flour, sawdust, corn flakes, popcorn and the like, have been proposed.

One characteristic feature of these heretofore used absorbents is that their porosity is uniform throughout, although the relative porosity of the various materials difiered. Inasmuch as there wasno way of modifyingthe porosity of a particular absorbent, a the above group by reason of its porosity factor occurring as near the desired point as possible. This naturally excluded from use many materials otherwise desirable.

It is important in explosives of the straight dynamite type where a liquid explosive compound such as nitro-glycerine is absorbed in a carrier, that the absorptive power of the carrier be such as to prevent exudation of the liquid explosive or segregation thereof in the package after manufacture.

Another important desideratum in the choice an absorbent is that if it is combustible, its chemical composition must be such that it will not upset the carbon-oxygen balance during combustion so as to leave greater than permissible quantities of carbon monoxide in the space following the explosion. Not all of the materials which otherwisermeet the necessary qualifications as an absorbent, have these characteristics.

For certain operations, it is desirable to have a comparatively large volume of explosive without, however, increasing the weight thereof or the disruptive force of the explosive charge. In such cases, explosives sired. For this reason, some absorbents are preferred over others because of their low density.

These carbonaceous material was chosen fromsuch, for instance, as bagasse pith, balsa wood, sphagnum moss and the like. One of the difficulties, however, with these fillers of exceptionally low density is that they have high absorptive power and, consequently, they either have a tendency to absorb too much of the liquid explosive or, if lesser quantities of the latter are used, the explosive propagation rate is lowered below a desirable limit.

Another important consideration from the standpoint of explosives containing nitroglyce erine is that in order to effectively initiate the explosion, a considerable quantity of the nitroglycerine must be instantly available to the detonator, that is, at the surface of the absorbent. Some absorbents, such as balsa and bagasse are bad from this standpoint because the nitroglycerine is completely contained within its pores and none remains on the surface of the cell Walls.

As a consequence, the combination is more insensitive than would ordinarily be desired.

Generally speaking, the ideal absorbent must be capable of absorbing large quantities of the explosive, where the explosive is of the nitroglycerine type it must be capable of leaving some of that substance at the surface, the absorbent must be capable of holding a liquid explosive without segregation or leakage, the absorbent must be stable and incapable of developing an acid or an alkaline reaction, for permissive ex plosives the absorbent must give a low density stick, the carrier should have a minimum amount of inerts which would show up as mineral ash while at the same time, the absorbent must be of a carbonaceous nature and capable of being burned during the explosion, without, however, disturbing to a marked degree the oxygen balance of the explosive composition. Another very important consideration is the ability to produce the carrier or absorbent having various sizes of pores therein. These pores may be uniform throughout the mass or they may vary within a single mass, as desired.

It has been discovered that the above properties are met to a maximum degree by artificially produced porous, carbonaceous masses made from plastics capable of having its degree of porosity controlled.

of a low density are de- I The present invention aims to overcome the above deficiencies by providing an absorbent which meets all of the desirable conditions, which has none of the undesirable characteristics, the porosity of which may be controlled during its manufacture to any desired point, even to the point of being modified in different parts of its bulk, which is readily combustible in and of itself and which, under the influence of the high temperatures usually attendant the explosion, W111 itself decompose or oxidize more readily than other absorbents heretofore used.

hyde condensation product in a dispersed form,

and removing the dispersing medium under such conditions that the collapse of the particles either can be prevented or regulated to form a porous gel. The porosity of the product may be regulated by regulating the temperatures attendant upon the removal of the dispersing medium. The production of products where the absorption varies on the same piece can be made principally in two different ways: either the jelly is heated to a higher temperature during the production, before the structure is solidified thoroughly, in which case the outer layer will collapse more or less, dependent upon temperature and humidity; or the finally hardened jelly is impregnated with water or aqueous solutions and quickly heated to a high temperature, whereby the outer layer collapses, whereas the inner part remains unchanged.

-An example of solid material as above produced has an apparent density of about 0.5 and on heating, decomposition commences at about 150 C. There is no melting point. The porous product has been found to have the ability of absorbing, approximately twice its weight in water. Nitro-glycerine (20% polymer) may be absorbed by the porous material in the form of a block in an amount equal to about twice the weight of the block. This value, of course, will vary with the viscosity of the nitro-glycerine. This absorption value corresponds to approximately 66%. The usual wood pulps have absorption values in the neighborhood of 'IOto 78% whereas balsa or bagasse may reach 85%. This condensation product is inert to alkali or alkaline earths encountered in explosive manufacture. These properties may be made to vary over rather wide limits by varying the method of production.

Moreover, the finished product may be ground to the desired degree of particle size where porosity is not particularly important and it is desired to take advantage of the desirable characteristics of the chemical composition of such condensation products as an explosive ingredient.

These condensation products also have the parti'cular advantage of being able to be produced in any desired shape.

Such a porous gel may be prepared by condensing urea and an'aqueous solution of form-' aldehyde in a ratio of 1 mol. of urea to two mols. of formaldehyde in a reflux apparatus. At the beginning of the condensation process, the solution should be maintained at a pH value of '7 or higher. After fifteen minutes of condensation, formic acid may be added in such an amount to bring the pH to the value of about 4.5, the congree dependent upon the degree of porosity desired, the greater the dilution the greater the porosity. The diluted solution may then be afterwards acidified by further additions of formic acid to a pH value of about 2-3 and subsequently allowed to solidify in closed containers. a particular shape is desired in the final mass, the container may take this shape. The gelation or solidification may occur at any desired temperature. After the desired degree of hardness has been obtained, the gel may be removed from the container and allowed to solidify at a temperature of about 20 0., dried at substantially 40 C., and then it may be followed by a drying temperature of 80 C. In those uses, where the presence of free acids or traces of formaldehyde are harmful, the gels may be washed with diluted ammonia solution either prior or subsequent to the final drying. Any excess ammonia or ammonia solution may then be eliminated by drying at 80 C.

As thus produced, the porous material may then be impregnated with any explosive salt and/or oxygen carrier such as ammonium, sodium or potassium nitrates or the alkali chlorates or perchlorates, and/or such liquid explosives as nitro-glycerine, nitro-glycols or mixtures thereof with or without additions of aromatic nitro densation continuing for about the period of an hour at this pH value. After the condensation is complete, the solution may be diluted to a debodies. Obviously such impregnation with salts may be in either sufiicient quantity to reduce the absorption of the liquid explosive to the desired value or in suflicient quantity to balance the condensation product with respect to the oxygen required.

A suitable method of impregnation with salts is to make a solution of the latter, 'absorb this solution in theporous material, followed by drying. Where liquid explosive materials such as nitro-glycerine or the like are used, they may be absorbed directly in the porous material. Obviously, the proportion of salts or liquid explosives to be combined with the porous material may vary within wide limits dependent upon the result desired, always keeping in mind, however, that the oxygen-carbon balance must not be unduly disturbed. This is a matter of simple chemical calculation.

Other fillers, such as wood meal, any of the usual vegetable material heretofore used, or even kieselguhr may be used as admixtures with the above combinations.

Where porosity is not of great consequence, the final porous material may be ground to a desired state of fineness and mixed with the above salts or liquid explosives in the desired propor.-'

tions with or without combustible fillers. In some cases, it will be found desirable to use a small quantityof comparatively long fibres such as bagasse or sisal to act as a binding agent between the particles and assist in making the eventual shape self-sustaining.

In the specification and claims, the term a urea is intended to include urea, thiourea, substituted urea or thiourea, derivatives thereof,

' mixtures of any of these compounds or any compound which, upon condensation with formaldehyde or equivalent aldehyde, may produce a suitable porous condensation product.

For the purpose. of this invention, any known process of production may be used. Furthermore, the combination 'of the before mentioned condensation with any of the known plastic products such as phenol-formaldehyde condensation products, is not precluded.

While the invention has been described with W here particular reference to a specific embodiment, it is to be understood that it is not to be limited thereto, but isto be restricted solely by the scope of the claims.

This application is a continuation in part of the applicants application Serial No. 128,985 filed March 4, 1937.

I claim:

1. An explosive comprising a porous condensation product of urea and formaldehyde and an explosive compound contained within its pores.

2. An explosive comprising a porous condensation product of urea and formaldehyde and a solid explosive compound contained within its pores".

3. An explosive comprising a porous condensation product of urea and formaldehyde and a liquid explosive compound contained within its pores.

4. An explosive comprising a porous condensation product of urea and formaldehyde and a solid and liquid explosive compound contained within its pores.

5. An explosive comprising a porous condensation product of urea and formaldehyde and ammonium nitrate absorbed therein.

6.- An explosive comprising a porous condensation product of urea and formaldehyde and an explosive nitro compound absorbed therein.

7. An explosive comprising a porous condensation product of urea and formaldehyde and nitro-glycerine absorbed therein.

8. An explosive comprising a porous condensation product of urea and formaldehyde and an oxygen carrier and a liquid sensitizer for said oxygen carrier absorbed therein.

9. The article of claim 1 in which the condensation product is of non-uniform porosity.

10. An explosive comprising an integrally formed shape of a porous condensation product of urea and formaldehyde and an explosive compound absorbed therein.

11. An explosive comprising a porous condensation product of a urea and formaldehydeand an explosive compound contained within its pores.

KURT E. RIPPER.