US2434879A - Process of preparing an explosive - Google Patents

Description

Patented Jan. 20, 1948 2,434,8'l9 raocEss or PREPARING AN EXPLOSIVEY George F. Wright, Henry H. Richmond, and Douglas 0. Downing, Toronto, Ontario, Canada, assignors to The Honorary Advisory Council for Scientific and Industrial Research, Ottawa, Ontario, Canada, a corporation of Canada No Drawing. Application July 16,1943, Serial No. 495,082

4 Claims. (Cl. 260-248) 1 The present invention relates to'a high explosive known as cyclonite and moreparticularly to a new and improved method of producing the same.

Cyclonite is an explosive of great power and brisance obtainable by the direct nitration (nitrolysis) of hexamethylene tetramine (hexamine) with concentrated nitric acid at about to 40 C. Within recent times an improved. method of preparing cyclonite was proposed by W. E. Bachmann in application Serial No. 495,078, filed July 16, 1943. According to the Bachmann procedure in one of its preferred embodiments, hexamine is treated at a reaction temperature above about 35 to 40 C. (Preferably at 60 to 90 C.) with an ammonia donor (e. g., ammonium nitrate) and concentrated nitric acid in the presence of a fatty acid anhydride-such as acetic anhydride, according to the overall equation 1) Hexamine+4HNOs+2NH4N03+6AczO= 2 cyclonite+12AcOH The reactants may be used in about the proportions indicated by Equation 1, but preferably with an excess of the nitric acid, ammonium nitrate and anhydride.

The process indicated by the overall Equation 1 involves the use of two solids (hexamine and ammonium nitrate) and two liquids (nitric acid and acetic anhydride. In order to obtain optimum yields of cyclonite by this process, the proportions of the reactants should be very carefully controlled to maintain the proper ratios throughout the course of the reaction. For this reason, portion-wise addition of the reactants to the reaction vessel is essential for optimum yields. Thus, in one of the modifications described in the above identified Bachmann application, the solids are introduced in approximately 100 separate, substantially equal portions.

It will be apparent that the foregoing procedure does not lend itself readily to large scale manufacture. It is therefore one of the objects I of the present invention to provide a commercially more feasible and expeditious method of carrying out the Bachmann process of producing cyclonite.

Another object is the provision of a method whereby proportionate quantities of the reactants (hexamine, nitric acid, ammonium nitrate and acetic anhydride) may be fed to the reactor in the form of liquids, thereby obviating the disadvantages arising from the use of one or more solid feeds.

Afurther object is to provide a modification of the Bachmann procedure for the production of cylonite, which lends itself to large scale manufacture.

Other objects and advantages will be apparent as the invention is hereinafter more particularly described.

, We have found that the foregoing objects may be accomplished by combining two of. the reactants to form a solution and by dissolving another of the reactants in a suitable solvent. More particularly, the improvement of the present invention involves the following modifications of the Bachmann procedure:

(1) Dissolving the ammonium nitrate required in the reaction, in the nitric acid, to form a solution which (after the evolution of a small amount of gas), ultimately becomes a clear liquid; p

(2) Dissolving the hexamine in a convenient amount of a substantially anhydrous liquid fatty acid such as glacial acetic acid or propionic acid;

(3) And then bringing (a) the clear ammonium nitrate-nitric acid solution, (1)) the hexamine-fatty acid solution and (c) the liquid fatty acid anhydride used in the process, into reactive relation under conditions suitable for the production of cyclonite.

It will be apparent that in the aboveprocess all of reactants charged to the reaction vessel are in the form of liquids, thereby obviating all the mechanical difficulties associated with the portionwise addition of'one or more solid feeds. In general, the reaction may be carried out under the conditions and with the proportions of reactants indicated above, it being understood, of course, that a sufficient amount of nitric acid and liquid fatty acid are used to dissolve all the ammonium nitrate and hexamine, respectively.

As previously indicated, the ammonium nitrate-nitric acid solution, when initially formed, evolves a small amount of gas which appears to be the oxides of nitrogen contained in the concentrated nitric acid. At any rate, the solution becomes clear if permitted to stand for a time, so that the nitric acid is in effect, purged of its yellowish color. The resulting clear solution may be used immediately, or stored (above 28 C.) for future use, with or without prewarming (from 28 C.) to the selected reaction temperature before being charged to the reaction vessel. The hexamine-glacial acetic acid solution also appears to be quite stable and may be used in a the present invention, a preferred embodiment will now .be described in detail. It .should besunderstood, however, that this is done solely by way of example, and is not to be construed as a limitation upon the spirit and scope of the appended claims.

Example 1.7 moles of acetic anhydride "was placed in -'a 1-liter 3-necked flask equipped with stirrer, thermometer, and suitable means for the introduction of two solutions from buret'tes. The flask was placed in a water bath iconld'zhe heated by steam, cooled with tap water 101' drained. To begin the reaction, the bath was heated to about 20 0. below the selected addition temperature (e. g., 60-,80 .C.) for the prewarmed reactants.

The two prewarmed solutions, one containing .48 mole ammonium nitrate in 1.11 moles of 9.7% nitric acid, the other, :24 nrole of hexamine in 160 cc. of glacial acetic acid, were introduced from the burettes in 30 alternate substantially stoic'hiometric proportions. The reaction temperature '(50-9U -(3., preferably 60 to 65 C.) was maintained at the selected point by suitable regulation of the bath temperature and the rates ofaddition,

After the reactants had all been added, the reaction mixture was stirred for a period of time (I) .to 60 minutes, preferably 15 to 20 minutes) at the selected reaction temperature and then diluted with v6 95i cc. of hot water, .after which the reaction mixture was allowed to stand at 2 5C. for four hours or more, then filtered and the precipitate washed with water. The crude yields ranged from about 75% to about 85% of the theoretical, based on overall Equation 1 above, the melting point of .the crude cyclonite varying from about 160 to 196 12,, depending on the reaction conditions.

The crude cyclonite was purified by dissolving the .cyclonite in boiling 50%, 150% or 70% nitric acid until the evolution of brown "fumes ceased and the boiling liquid was coloredpale yellow or yellow-orange. In most cases, boiling for 5 to minutes was required. The clear solution was then diluted With an equal volumeof water, and after cooling, the solid was filtered, washed with water and dried to constant weight at 70 .C. This treatment raised the melting point to around 2il0 C.

One of the indirect advantages of theprocess of the present invention arises from the fact that a nitric acid solution of ammonium nitrate is much less rapidly corrosive to the flesh than concentrated nitric acid itself. Thus the solution, if promptly flushed with water from the flesh, does not produce the characteristic yellow coloration and painful burn caused by 98% nitric acid.

It may ?be mentioned {that certain changes in the foregoing procedure give results which are far less satisfactory. Thus if the hexamine is dis- .solved in the acetic anhydride (instead of using .glacial acetic acid). the yield is definitely inferior (for example, 18%) .It will be apparent that the foregoing procedure lends itself :a'dmirably to the production of cyclonite in the apparatus described and claimed in the depending application of David C. Hull, Ser'iaTNo. 495,083,1iled July 3, 1944. Other variations and applications of the present invention will be apparent to those skilled in the art. We therefore intend to be limited only in accordance Withthe following patent claims.

We claim:

.1. honethod of producing cyclonite'which loomiprises forming =a:solution of-ammonium nitrate in nitric acid and a solution of 'hexamine substantially anhydrous liquid fatty acid, feeding said solutions in alternate portions into liquid fatty "acid anhydride, and maintaining the reaction temperature between 50 and C.

A method of producing cyelonite which comprises forming a solution of ammonium nitrate in nitric acid and a solution of hexamine in -gla cial acetic acid, feeding said solutions in substantially s'toichiemetric proportions in alternate portions into acetic anhydride and maintaining the reaction temperature at about 60-65 3. a method as defined in claim 1 wherein said solutions and said acid anhydride are prewarmed to reaction temperature before being brought into reactive relation.

4. A method as defined in claim 1 wherein said solution of ammonium nitrate in nitric acid is allowed to stand until the evolution of gas therefrom ceases before .feeding it into the .acid -an "hydride.

GEORGE F. WRIGHT.

DOUGLAS (3. DOWNING.

REFERENCES CITEB The following references are of record in the file of patent:

Name

GTHER REFERENCES Tanner, Chemical and Me'tallurgi cal Engineering, vol. 29, No. 10, page 404.