US3434895A - Process of preparing a particulate nitro-cellulose-containing explosive - Google Patents

Description

United States Patent 3,434,895 PROCESS OF PREPARING A PARTICULATE NITRO- CELLULOSE-CONTAINING EXPLOSIVE Jean P. Picard, Morristown, and H. William Voigt, Jr.,

Stanhope, N.J., assignors to the United States of America as represented by the Secretary of the Army No Drawing. Filed May 12, 1967, Ser. No. 638,711 Int. Cl. C06c 1/00, 5/00; C06b 19/02 U.S. Cl. 149-27 5 Claims ABSTRACT OF THE DISCLOSURE The invention relates to a process for preparing a particulate explosive comprising lead oxide and silicon encapsulated with nitrocellulose which comprises dispersing nitrocellulose, red lead oxide and silicon in N-methyl- 2-pyrrolidone and precipitating said explosive composition with water. Said explosive composition may be admixed with lead styphnate and used in fuzes.

This invention relates to an explosive composition and a method of rendering the same safe for further processing.

In the past, it has been found that a specific composition containing lead styphnate and nitrocellulose was highly effective as an explosive propelling medium for use by the armed services in chemically oriented fuzes. However, it was found that the composition was very hazardous to manufacture. For instance, the composition must be manufactured in such a manner that it is in the fine powdery state of a specific size to insure a clean state of explosive of a specific duration due to the requirements of fuze design of a specified explosive device.

The first method of rendering a mix in such a state consisted in dispersing the ingredients of the composition throughout an acetone medium with subsequent evaporation to produce a solidified mass. However, to render the mix into the state where it might be utilized in a fuze, it was found necessary to physically break the mass into particles of finer size. This resulted in explosions and was extremely hazardous to both personnel and equipment.

The second method devised consisted in deleting the most sensitive agent, lead styphnate, from the mix prior to processing in the manner set forth above. However, it was found that nitrocellulose, a relatively non-sensitive ingredient of the combination, was rendered highly sensitive due to the above process and was quite hazardous to process to the size desired.

It is therefore an object of this invention to provide a process of manufacture of an explosive combination in a specific configuration of the size desired, said process being simple, inexpensive and especially non-hazardous to operating personnel or adjacent equipment.

Another object is to provide a chemical combination of a specific configuration such that particles of lead oxide and silicon are individually, or in combination, encapsulated by a thin, hardened shell of nitrocellulose for a specific explosive chain reaction, of a desired interval in time, throughout the entire mass by detonation.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following description:

The explosive chemical combination, with which we are concerned, contains nitrocellulose, with or without desired stabilizers, and chemical filling agents such as lead oxide, and particles of silicon.

The process of this invention comprises dispersing the above specific explosive combination in a solvent such 3,434,895 Patented Mar. 25, 1969 as N-methyl-Z-pyrrolidone and thereafter precipitating the entire combination from such solvent by the use of water, at which point, the precipitate may be gathered in any one of a number of conventional manners known in the art.

In theory, the nitrocellulose, with or without one or more stabilizers, forms a dispersed colloidal system with the N-methyl-Z-pyrrolidone, while the lead oxide and silicon are merely dispersed in the fluid system. However, upon precipitation of the chemical combination and its entirety by water, the nitrocellulose encapsulates the lead oxide and silicon, individually or in combination, and is hardened by the action of the water.

The precipitate produced may be washed, if desired, one or more times to insure the hardness of the encapsulating explosive material surrounding the chemical fillers of the specific combination. Further, subsequent to the procedure described, the precipitate, with or without washing, may be given a drying treatment to insure the individual integrity of the particles.

The precipitate resulting from this procedure has been found to be of the size desired for use, in admixture with lead styphnate, in fuzes of chemically oriented design as a time-delay composition of specific duration.

The following are typical examples of the process of the present invention:

Example I 2.0 gms. of nitrocellulose powder, having nitrogen content of 12.6% and stabilized with 0.04 gm. of Z-nitrodiphenyl amine, 4.6 gms. of silicon powder and 18.3 gms. of lead oxide were dispersed with stirring throughout 40 mls. of a N-methyl-Z-pyrrolidone solvent. Subsequently, 50 mls. of water were added to the dispersion and the resulting precipitate is collected.

Example II 8.173 gms. of nitrocellulose powder, dampened with ethanol, and stabilized with 0.167 gm. of 1,1-diethyl-3,3- diphenyl urea were dispersed, with stirring, throughout mls. of N-methyl-Z-pyrrolidone. The dispersed powdery ingredients form a clear colloidal solution with the solvent in a relatively short time, at which time, 18.35 gms. of silicon powder and 73.31 gms. of red lead oxide were then added to the colloidal solution with stirring to form a uniform dispersion. Subsequently, 200 mls. of water were added to the above resultant dispersion and the dispersed material was thereupon precipitated. The resulting slurry was then filtered utilizing a Biichner funnel and a No. 54 high-wet strength paper. The filter cake was then washed with 200 mls. of water and air-dried over a steam bath until a constant weight was finally achieved.

Example III The process of Example 2 wherein 1,1-diethyl-3,3- diphenyl urea was replaced with 4-nitro-N-methyl aniline as a stabilizer for nitrocellulose.

As is evident from the above, a convenient yet safe process has been developed to prepare a uniform, finely divided and free-flowing composition from the combination described. The resulting powder may then be dryblended with lead styphnate without hazard to produce a specific composition called for by military specifications for chemical oriented fuzes.

The unique composition produced by the present process is a clean burning mass which does not leave a residue on decomposition due to a substantial evolution of oxygen. Therefore, there is no residue that will interfere with the operation of the fuze. Nitrocellulose, the encapsulating material, when ignited, evolves oxygen and provides the intense heat necessary to initiate the burning 3 of the lead oxide and silicon. The red lead oxide also evolves oxygen and insures an intense heat for a sustained period while the silicon retards the burning rate of the nitrocellulose and any lead styphnate which may be physically mixed with the composition.

The size of the powdery material which is produced by the process of the present invention is in the range of up to about 5 microns. However, it is preferred to produce particles in the range of about 1 to 2 microns in size. Particles of a larger dimension tend to have an uneven burning characteristic and are unreliable in the detonation process. In the process, as described above, the nitrocellulose precipitate produced is very finely divided and therefore produces more surface area for utilization in encapsulating the fillers described. This affords a more uniform distribution of the nitrocellulose throughout the mass and tends towards a more reliable deflagrating ability. This encapsulating process may be controlled to give a specific burning duration for the particles produced.

Due to the above process, nitrocellulose of varying molecular weight may be utilized to produce a more desirable product with respect to aging and storage. Also, a composition, which is prepared from nitrocelluose of relatively high molecular weight, is generally more heat resistant and safer to work with.

Obviously, many modifications and variations of the present invention are possible in light of the above teaching. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

We claim:

1. A process wherein an explosive composition is prepared for use in a fuze comprising dispersing a composition containing nitrocellulose, red

lead oxide, and silicon in a solution of N-methyl-Z- pyrrolidone precipitating said composition from said dispersion with water, and collecting said precipitate.

2. The process of claim 1 wherein said collected precipitates are admixed with lead styphnate.

3. The process of claim 1 wherein said nitrocellulose is dissolved and red lead oxide and silicon are dispersed in N-methyl-Z-pyrrolidone.

4. The process of claim 1 wherein said precipitate is washed with a surplus of water prior to collecting the same.

5. The process of claim 1 wherein said precipitate is dried and passes through a 35 mesh screen.

References Cited UNITED STATES PATENTS 2,497,387 2/1950 Zenftman 149-38 X 2,587,694 3/1952 Chalmers et al 149-38 X 2,988,438 6/1961 Allovio 14944 X FOREIGN PATENTS 310,509 6/1930 Great Britain.

LELAND A. SEBASTIAN, Primary Examiner.

US. Cl. X.R. l496, 38, 100