US2168563A - Nitrostarch explosive - Google Patents

Description

Patented ug. 8, 193% NITROSTARCH ELOSIVE Clyde Oliver Davis, Woodbury, N. 5., assignor to E. I. du Pont de Nemours & Company, Wilmington, 1121., a corporation of Delaware No Drawing. Application March 8, 1938, Serial No. 194,606

4 Claims.

many disadvantages as to discourage its use. An

outstanding disadvantage .of the use of nitrostarch in explosives has been the extreme insensitiveness to propagation of the resulting compositions. Nitrostarch also has the disadvantage that it is highly sensitive to accidental initiation by means of sparks, friction, and shock. A further undesirable feature has been the difllculty in manufacturing and handling nitrostarch and the explosives containing same due to the extreme dustiness of these materials.

The object of the present invention is a new and improved nitrostarch explosive. A further object is a nitrostarch explosive with improved sensitiveness to propagation, in whlch ammonium nitrate is an important constituent. Another objeet is a nitrostarch explosive of improved stability against unintentional initiation by impact. An additional object is a-new and improved process for producing explosives comprising nitrostarch and ammonium nitrate.

Other objects will be apparent from the following detailed description of my invention.

I have found that the foregoing objects are ac-- complished and the foregoing disadvantages overcome by the process of my invention which com-1 prises dissolving ammonium nitrate in substantiallya'nhydrous liquid ammonia, dispersing in said solution, nitrostarch as a sensitizing ingredient, expelling the free ammonia and thereby I 850 grams of ammonium nitrate was ,intro duced into a jacketed graining kettle equipped with agitation means. 150 grams of nitrostarch was added, and the mixer was closed.- 250 grams of anhydrous liquid ammonia was then run into the graining kettle and the agitation of the mixer was maintained during the solution of the ammonium nitrate. The free ammonia was then expelled by heating the charge to 3 0-35 0., with final evacuation under reduced pressure. The agitation was continued during thedrying, so that a dry, loose product resulted, comprising minute regions of nitrostarch disseminated within crystals 01 ammonium nitrate. The explosive composition was punched into cartridges of such density that 153 c rtridges were contained in a 50-lb. case. This where full sticks were used without removal of crimped ends, and a velocity of detonation of 3670 m/sec.

Eramplez 830 grams of ammonium nitrate was introduced into a jacketed graining kettle in the same manner as in Example 1. 150 grams of nitroplosive showed a sensitive-' ness of 7 inches by the double-cartridge test,

starch was then added, together with 20 grams of a foam-suppressing mixture, and the mixer closed. 250 grams of anhydrous liquid ammonia was run into the graining kettle, and'the incorporation of ingredients and preparation of the dried product were carried out as in Example 1. The finished explosive composition was punched into cartridges running 148 to the 50-lb. case, and showed a sensitiveness of 6 inches, and a velocity of 3830 m/sec.

Example 3 400 grams of ammonium nitrate was introduced into a jacketed graining kettle. as in Example 1, together with grams of nitrostarch. Sufficient anhydrous liquid ammonia was run into the graining kettle to dissolve all the ammonium nitrate, and form a substantially saturated solution, and 520 grams of coarsely granulated ammonium nitrate was also introduced into the kettle. After incorporation with the ingredients, the free ammonia was expelled as in Example 1, and a. dry product obtained. This explosive composition was punched into cartridges such that per 50-lb. case resulted. The explosive showed a sensitiveness of 1 inch by the double-cartridge test and a velocity of detonation of 1345 m/sec.

The compositions prepared according to my invention and illustrated in the foregoing examples may be employed as explosives either by themselves, or blended with other materials to obtain the desired oxygen balance, as well as to control other explosive properties. For instance,

other conventional ingredients may be added, such as nitrate of soda and the common combustibles; viz., ground coal, starch, and meals. It will be understood that various degrees of sensitiveness may be obtained, depending on the relative proportions of ammonium nitrate and nitrostarch employed. In many cases it may be desirable to introduce a so-called foam-prevention agent to suppress foaming during the expulsion of the free ammonia. As examples of such agents, I may cite oleic acidor lard oil.

The present process brings many advantages in the preparation of such nitrostarch compositions and allows the use of proportions of materials which would not be possible otherwise for obtaining the desired properties.

The outstanding advantage of my invention is the fact that nitrostarch explosives having highly enhanced sensitiveness to propagation are prepared thereby. These explosives have a further advantage over nitrostarch explosives of the prior art in that they exhibit a decreased sensitiveness to unintentional initiation by sparks, friction, and incidental shock. Furthermore, the preparation of nitrostarch explosives by my improved ammonia process eliminates all dust during manufacture and the hazards attendant therewith.

These advantages of enhanced sensitiveness to propagation and stability against impact are demonstarted quantitatively in the following table.

Incorporation Ingredients and properties ggg g eg according to ventgsnal the process of. method the present invention 1 Percent nitrostarch l5 l5 2 Percent ammonium nitrate 85 85 3 Full stick sensitiveness test in inches 2 6 4 Stability against impact 120 995 according to the process of the present invention.

The widely divergent properties resulting from these two methods of incorporation are shown in the horizontal columns 3 and 4. The sensitiveness of the explosives to propagation was readily determined by the full stick sensitiveness test. Horizontal column 3 indicates the results of this full stick sensitiveness test as applied to both compositions. This test may be defined as the maximum width of air gap across which propagation of the detonation wave will occur between full sticks or cartridges placed in line lengthwise without removal of the crimped ends. This distance is expressed in inches in the foregoing table.

Thus, it is shown that the nitrostarch explosive according to the present invention is more sensitive to propagation than the explosive of the art, in a ratio of 6 to 2.

Horizontal column 4 shows the results o e test for determining stability against initiation by impact, In this test a weight is permitted to fall from a, measured height upon the powder to be tested, and the minimum height is determined at which the powder fails to detonate in 10 falls of the weight. The result is expressed in the terms of the impact, defined as the height in inches multiplied by the weight in pounds.

In the application of this test to the foregoing powders, it will be noted in column 4 of the table that the nitrostarch explosive according to the present invention, exhibits increased stability over the explosive of the art in a ratio of 955 (impact) to 120.

The importance of these enhanced properties of my explosive thus quantitatively demonstrated, will be clear. to any explosive technologist.

A further advantage resulting from my process of preparation comes in the better control of sensitiveness of the finished explosive to intentional initiation. As prepared by my invention, the compositions have an excellent degree of sensitiveness such as has been obtained by no previous method of preparation. By use of my method, a given sensitiveness value can be obtained by the employment of smaller percentages of nitrostarch, and at the same time greater uniformity of product results.

In my co-pending application Serial No. 194,- 551, filed March 8, 1938, I have disclosed my ammonia process as applied to the manufacture of explosive compositions generally. It will be understood that, in the present application, I intend to claim only a preferred type of explosive; namely, an improved nitrostarch explosive as prepared by the ammonia process.

Many difierent embodiments of this invention may be brought about without departing from the spirit and scope thereof. I wish, therefore, to be limited only by the following patent claims.

I claim:

1. A nitrostarch explosive comprising particles of nitrostarch dispersed within crystals of ammonium nitrate, having an enhanced sensitiveness to propagation and decreased sensitiveness to unintentional initiation as the result of crystallization from substantially anhydrous liquid ammonia.

2. The process of preparing a nitrostarch explosive of improved sensitiveness to propagation and decreased sensitiveness to unintentional initiation, which comprises dissolving ammonium plosive of improved sensitiveness to propagation,

which comprises dissolving ammonium nitrate in substantially anhydrous liquid ammonia, dispersing nitrostarch in said solution, together with a small percentage of a foam-suppressing agent, and expelling the free ammonia there from.

CLYDE OLIVER. DAVIS.