US3553039A - Ammonium perchlorate-ammonium nitrate explosive composition containing excess chloride ion - Google Patents

Abstract

AN AMMONIUM PERCHLORATE EXPLOSIVE COMPOSITION COMPRISING AMMONIUM PERCHLORATE, AT LEAST 5% BY WEIGHT OF AMMONIUM NITRATE, AT LEAST 0.003% BY WEIGHT OF A METAL AND AT LEAST ONE CHLORIDE ANION PER METAL ATOM IN EXCESS OF THE RATIO OF CHLORIDE ANION TO METAL ATOM THAT WOULD BE OBTAINED BY ADDING THE METAL AS ITS CHLORIDE SALT.

Description

Jan; 5, 1971 A. G. KEENAN ETAL AMMONIUM PERCHLORATE-AMMONIUM NITRATE EXPLOSIVE COMPOSITION CONTAINING EXCESS CHLORIDE ION Filed July 15, 1968 A nUov UEDEQ Qua EMC.

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ARTHUR GKEENAN If IVENTORS TIME (MIN) AT TO RN EYS United States Patent AMMONIUM PERCHLORATE-AMMONIUM NI- TRATE EXPLOSIVE COMPOSITION CON- TAINING EXCESS CHLORIDE ION Arthur G. Keenan and Robert F. Siegmund, Miami, Fla., assignors to Research Corporation, New York, N.Y., a nonprofit corporation of New York Filed July 15, 1968, Ser. No. 744,989 Int. Cl. C06b N04 US. Cl. 14941 4 Claims ABSTRACT OF THE DISCLOSURE An ammonium perchlorate explosive composition comprising ammonium perchlorate, at least 5% by weight of ammonium nitrate, at least 0.003% by weight of a metal and at least one chloride anion per metal atom in excess of the ratio of chloride anion to metal atom that would be obtained by adding the metal as its chloride salt.

This invention relates to ammonium perchlorate gas producing or explosive compositions, and more particularly to ammonium perchlorate compositions having an improved decomposition rate.

Ammonium perchlorate is used as an oxidizer in propellants and other explosive compositions. Various combustion catalysts have heretofore been added singly or in combination to ammonium perchlorate in order to improve its decomposition characteristics. We have now discovered that the decomposition of ammonium perchlorate is greatly improved by adding ammonium nitrate, a metal, and an excess of chloride anions with respect to the amount of metal added.

More specifically, the present invention is an ammonium perchlorate explosive composition comprising ammonium perchlorate, at least 5% by weight of ammonium nitrate, at least 0.003% by weight of a metal and at least one chloride anion per metal atom in excess of the ratio of chloride anion to metal atom that would be obtained by adding the metal as its chloride salt.

The composition of the present invention is made by incorporating ammonium nitrate, the metal or metal-containing additive and the chloride anion-containing additive into ammonium perchlorate, generally by milling or dry mixing the ingredients. The resultant mixture may be shaped or pressed or otherwise prilled to the form of compacted grains.

The metal may be added as the free metal, or, preferably, in combined form. It is generally most convenient to use a readily available salt containing the metal as a cation or as part of the anion. A list of such suitable salts would include nitrates, carbonates, sulfates, chromates, dichromates and the like. The metal may also be present in both the cation and anion as, for example, copper chromite.

The decomposition characteristics of ammonium perchlorate are improved by the incorporation of at least 0.003% of a metal provided ammonium nitrate and excess chloride anion are also present as more fully discussed below. The beneficial effect of metal addition increases with increasing the metal content of the composition until either the diluent effect and/ or the decreasing solubility of the metal and chloride-containing additives tend to exhibit a contrary effect. There is no theoretical upper limit for the amount of additives which may be employed since these adverse factors vary widely with the particular additives employed. Satisfactory explosive compositions containing as high as 5% by weight of metal and excess chloride anion have been prepared and tested. It is doubtful that compositions in which the amount of metal and chloride additive exceeds 5% by weight of the composition would be useful in practice except possibly in Very special situations.

The rate of improvement obtained using metal-chloride combustion catalysts in an ammonium perchlorate composition according to the present invention with various metals was determined by thermographic analysis. In order of decreasing effectiveness, the metals are:

Chromium Titanium Copper Lead Silver Manganese Nickel Mercury Iron Bismuth Gold Platinum Palladium Zinc Cobalt Cadmium Cerium Aluminum Zirconium Metals listed in the first column are particularly effective. Metals having a standard oxidation potential above 2.0 volts, i.e., the alkali metals such as lithium, potassium, sodium, et cetera, are much less eifective.

The composition according to the present invention should also contain at least one and preferably ten chloride anions per metal atom in excess of the ratio of chloride anion to metal atom that would be obtained by adding the metal as its chloride salt. The decomposition characteristics of the composition improve, but to a lesser extent, as 30-40 chloride anions per metal atom are added. Relatively little further improvement is noted as additional chloride is provided. The particular salt employed as the chloride carrier is not determinative; the chlorides of sodium, potassium and ammonium are preferred because of their ready availability at low cost.

The beneficial effects of metal and excess chloride anion addition on the decomposition rate of ammonium perchlorate are not obtained unless ammonium nitrate is added as well. Generally speaking, compositions containing at least about 5% and preferably about 5-15 by weight of ammonium nitrate give the best results. The amounts of the various additives to be provided are interrelated since the minimum amount of a given additive required depends on how much of the others is present. For example, the minimal concentrations of metal and chloride may be decreased somewhat by increasing the amount of ammonium nitrate added; the minimal concentration of the metal may be decreased by increasing the amount of chloride added. It is apparent that compositions containing minimal amounts of the metal would be the most desirable in practice. One of the advantages of the present composition is that they require less of the metal-containing additive than is generally employed in ammonium perchlorate explosive or propellant compositions.

The shortening of the induction period and the improved decomposition of ammonium perchlorate obtained according to the present invention were measured by thermographic analysis. Compositions containing ammonium perchlorate, ammonium nitrate, and a metal salt, with or without added sodium chloride, were prepared and weighed into glass reactor tubes and placed in a furnace programmed to maintain a constant temperature of 295 C. The more active samples deflagrated on reaching about 250 C.; the others decomposed just prior to reaching furnace temperature.

The curves shown in FIGS. 1 and 2 of the drawing are graphs of temperature against time as measured by a thermocouple set in the test compositions. Curve A is the thermograph obtained on a test composition containing parts by weight of ammonium perchlorate, 10 parts by weight of ammonium nitrate and 0.0135% by weight of potassium dichromate. Only a partial decomposition and moderate temperature rise occurred leaving a residue of about 70% undecomposed material. Curve B shows the results on a similar composition except that 0.16% by weight of sodium chloride was added. Complete decomposition occurred sending the temperature otf scale. The test composition of curve C contained 85% ammonium perchlorate, 15% ammonium nitrate and 0.03% by weight of potassium dichromate. Even though the amount of nitrate and dichromate was greatly increased over that present in the composition of curve A, no significant improvement in decomposition was obtained. The test composition of curve D contained 92 parts by weight of perchlorate, 8 parts by weight of ammonium nitrate, 0.015% by weight of dichromate and 0.23% by weight of sodium chloride. Even though the amounts of nitrate and dichromate were less than that of the composition of curve C, the addition of chloride gave an extremely strong decomposition. Similar results were obtained with compositions containing 942 parts We claim:

1. An ammonium perchlorate explosive composition comprising ammonium perchlorate, at least 5% by weight of ammonium nitrate, at least 0.003% by weight of a metal and at least one chloride anion per metal atom in excess of the ratio of chloride anion to metal atom that would be obtained by adding the metal as its chloride salt.

2. A composition according to claim 1 wherein the metal is chromium, copper, silver, nickel, iron, gold, palladium, cobalt or cerium.

3. A composition according to claim 1 containing 5-15 by weight of ammonium nitrate and at least ten chloride anions per metal atom.

4. An ammonium perchlorate explosive composition comprising 90 parts by weight of ammonium perchlorate and 10 parts by weight of ammonium nitrate, 0.0135 by weight of potassium dichromate and 0.16% by weight of sodium chloride.

References Cited UNITED STATES PATENTS 3,336,171 8/1967 Keenan et al. 149-43 CARL D. QUARFORTH, Primary Examiner S. J. LECHERT, JR., Assistant Examiner US. Cl. X.R. 14942, 43, 46, 76

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