US3475236A

US3475236A - Non-aqueous cap-sensitive explosive containing gelled nitromethane and inorganic nitrate oxidizer salt

Info

Publication number: US3475236A
Application number: US729479*A
Authority: US
Inventors: Garland H Walker; Carlos E Ballard
Original assignee: Seispower Corp
Current assignee: Seispower Corp
Priority date: 1968-04-17
Filing date: 1968-04-17
Publication date: 1969-10-28
Anticipated expiration: 1986-10-28

Description

G. H. WALKER ET A Oct. 28, 1969 3,475,236

NON-AQUEOUS CAP-SENSITIVE EXPLOSIVE CONTAINING GBLLED NITROMETHANE AND -INOBGAN1C NITRATE OXIDIZER SALT Filed April 17, 1968 ZOELWOlZOU MEDICCE mm 00 mm cm nh on mm 00 mm on n 0* mm on nN 0N n O n O ON nN Om WM 0? m? Om mm 0m 0w Ch mh Om mm 00 mm Mr. R Mm Wm. 5W 5 w a. C

- 6 a/ ao-LDVJ agMod 0/ an Wa/A er 4 4a mel WAN 9 MQRLQM YATTORNE YS United States ABSTRACT OF THE DISCLOSURE An explosive including a nitrate or nitrates sensitized with gelled nitroparaflin, which has a substantially permanent shelf life, is economical, is blasting-cap sensitive, and provides high energy detonation.

BACKGROUND OF THE INVENTION The field of this invention relates to explosives. In the past, ammonium nitrate has been sensitized with liquld nitromethane, but due to evaporation and separation, such mixture has had a very short shelf life. Nitromethane has been available in a gelled form, the gelling usually being accomplished by mixing the nitromethane with nitrocellulose or other gelling agents such as disclosed in United States Patent No. 2,954,350. As disclosed in United States Patent No. 3,338,165, it was thought that stability in a gelled nitromethane explosive could be obtained by incorporated therewith resin balloons or microballoons, a product described in said Patent No. 3,338,165, and more specifically described in Patent No. 3,101,288. When using such gelled nitromethane with the resin balloons, ammonium nitrate Was added in small quantities as ancillary to the explosive merely for serving as an oxidizer.

It has been found that gelled nitromethane with resin balloons actually has a short shelf life, with substantial separation occurring in a period of thirty to fifty days. When such separation occurs, the expolsive can usually no longer be detonated. Additionally, resin balloons are expensive for an explosive, and this has limited the usefulness of the gelled nitroparafiin explosives heretofore known.

SUMMARY OF THE INVENTION The present invention resides in an explosive which is substantially permanent in that substantially no separation of the components occurs, thus providing a substantially permanent shelf life over a period of years. It has been found, quite unexpectedly, that such stability can be obtained by sensitizing nitrates such as powdered or prill size ammonium nitrate with gelled nitroparafiins such as nitromethane, and that resin balloons are not necessary for producing a high energy detonation with such components. Since ammonium nitrate is inexpensive, as compared to resin balloons, the explosive of this invention is remarkably inexpensive. Furthermore, it was surprising to learn that high energy detonation can be obtained with either gelled or liquid nitromethane in the minority as compared to the nitrate in the composition, whereas previously they had always been used in at least equal amounts. Since ammonium nitrate costs far less than gelled nitromethane, the cost of the explosive of this invention is low while still obtaining a high energy explosive.

BRIEF DESCRIPTION OF THE DRAWING The drawing is a graph illustrating the relative energy levels of the composition of the present invention in designated percentages of the constituents.

atent O 3,475,236 Patented Oct. 28, 1969 DESCRIPTION OF THE PREFERRED EMBODIMENTS Basically, the explosive of this invention is a mixture of gelled nitroparaflin and one or more nitrates. The nitroparafiin and the nitrate are mixed together in any known type of mixer such as a ribbon blender, paddle mill, or similar equipment so as to disperse the gelled nitroparaffin substantially uniformly with said nitrate to thereby form a substantially permanent mixture which has a long shelf life, is economical, is blasting-cap sensitive, and which provides high energy when detonated.

The term nitroparafiin as used herein includes nitromethane, nitroethane, l-nitroprop-ane, and 2-nitropropane. Each of such nitroparafiins is gelled by the use of a gelling agent such as nitrocellulose. Another gelling agent is one sold under the trademark Gantrez by General Aniline and Film Company and which is chemically known as methyl vinyl ether. Other gelling agents are disclosed in United States Patent No. 2,954,350 and are referred to in United States Patent No. 2,338,165. Although the percentage of the gelling agent will vary, the gell should be thick enough so that it does not readily pour, but it should not be difiicu t to distribute thoroughly throughout the ammonium nitrate or other nitrate used in making the explosive of this invention. Where nitrocellulose is used for gelling nitromethane, the nitrocellulose is present in an amount from about one percent to about ten percent by weight, the balance being nitromethane. The same relative proportions may be used with other nitroparaffins.

In obtaining the results indicated on the chart or graph shown in the drawing, the gelled nitroparafiin was a mixture of four percent nitrocellulose and ninety-six percent nitromethane. The explosive mixture of this invention was also made with a gelled nitroparaffin wherein the nitroparaffin was nitromethane and was mixed with approximately two percent by weight of nitrocellulose, and another test was made wherein the nitrocellulose was present in an amount of about eight percent by weight while the nitromethane was present in an amount of about ninetytwo percent by weight. It is preferred that the nitromethane or other nitroparafiin be gelled using approximately two percent by weight of nitrocellulose, although as stated above, the exact percentage and the particular gelling agent may be varied by those skilled in the art so as to obtain a gelled nitroparaflin of adequate consistency for thorough mixing with the ammonium nitrate or other nitrate forming the explosive of this invention.

Although ammonium nitrate is preferred in the explosive of this invention, either sodium nitrate or lithium nitrate may be used in place of ammonium nitrate, or a mixture of any two or more of such nitrates may be used. Normally, the nitrates are received from the manufacturer in prill size which is generally about one-sixteenth of an inch or one-eighth of an inch in diameter. It has been found that ammonium nitrate and the other nitrates are effective as a high energy explosive when they are in such prill size, but when the nitrate or nitrates are reduced to a powdered condition, normally about 500 microns in size, then the explosive is more easily detonated and produces a higher energy level when detonated. The term powdered has been used herein to designate the relatively finely divided or pulverized nitrate in the explosive of this invention so as to distinguish same from the prill. size. It should also be noted that the listed nitrates are the only ones known to be operable in the explosive of this invention, but it will be understood that equivalents thereof should be included within the scope of this invention.

Referring now to the graph shown in the drawings, such graph was made by conducting a series of tests with different percentages of gelled nitromethane and ammonium nitrate. Thus, the upper row of numerals above the Mixture Composition in the drawing refers to the percentage by weight of the gelled nitromethane, whereas the lower set of numerals refers to the percentage by weight of ammonium nitrate. On the left of the chart, the power factor is indicated with numerals running from 1 to 8. Such power factor is merely a comparative scale with the numeral 4 designating the energy level for sixty percent strength dynamite which is recognized as a high energy explosive.

Tests were run with samples at each point on the graph starting with ninety-five percent gelled nitromethane and five percent ammonium nitrate and going to the opposite end of the chart where the sample had five percent gelled nitromethane and ninety-five percent ammonium nitrate. Each of the test samples consisted of fifty grams by weight of the mixture composition in a two inch diameter paper or plastic cup. The tests were conducted under varying conditions, including exploding same behind safety shields, in an open field, and under water. The results were essentially the same for each of such conditions, and the energy level was as indicated by the graph in the drawing. The ammonium nitrate was present in prill size in one series of tests, in the powdered condition, approximately 500 microns, in another series of tests, with the ammonium nitrate ranging from five percent to ninety-five percent. The results in each of such test samples were as indicated on the graph in the figure of the drawing.

The surprising result obtained is reflected on the graph wherein it is seen that a relatively high energy level is obtained when the base mixture of nitroparafiin and a nitrate or nitrates are in the mixture range of from about ten percent to about thirty percent nitroparafiin and from about ninety percent to about seventy percent ammonium nitrate, or other nitrate, such percentages being by weight. The energy obtained is comparable to much higher percentages of the nitroparaffin and is even higher than when the base composition includes approximately forty percent nitroparafiin and sixty percent ammonium nitrate. It is even more surprising to find that when the base explosive mixture of this invention included twenty percent nitroparatfin by weight and eighty percent nitrate by weight, the explosive energy level was even higher than when the constituents were mixed in equal parts, such dilference being reflected on the graph. In view of the relatively low cost of ammonium nitrate as compared to the nitroparaflins, this result is very important since the explosive thus provided is a high energy level explosive with a very low cost. When the nitroparafiin is of the gelled type, the shelf life of such explosive is substantially permanent. Even when the liquid nitroparafiin is utilized instead of the gelled nitroparafiin, the same results as reflected by the graph in the drawing are obtained, but the advantages of the substantially permanent shelf life are not obtained.

Various combinations of nitrates with nitroparafiin were tested and the same curve as shown in the figure of the drawing resulted, although the energy level of the curve was lowered with nitrates other than ammonium nitrate. Thus, the curve reflects the energy levels obtained using ammonium nitrate as the nitrate and nitromethane as the nitroparafiin, but the same curve and results are obtained as shown in the graph, using the other nitroparaffins and other nitrates, but the level of energy is reduced to some extent, depending upon the particular components. For example, using sodium nitrate in place of ammonium nitrate, or using lithium nitrate in place of ammonium nitrate, produces the same curve but at a lower level at each point, with the lithium nitrate curve being lower than that of sodium nitrate. Various combinations of the nitrates were also tested in the same manner as described above. For example, samples were made up in different amounts starting with equal percentages of ammonium nitrate and sodium nitrate and varying each sample by ten percent up to 100 percent sodium nitrate and up to percent ammonium nitrate, with the balance in each case being the other nitrate. Each of such samples was tested in mixture with nitromethane and the other nitroparaffins at the various percentages indicated on the graph of the drawing and the same curve resulted but at a lower energy level.

In another test, the resin balloons or microballoons referred to in United States Patent No. 3,338,165, identified above, were added to the base mixture of the gelled nitromethane and ammonium nitrate, but no improvement in the explosive energy was obtained, and the results of such explosive tests at the various sample percentages indicated in the chart of the drawings produced the curvature as shown in the drawing. By way of specific example, the microballoons were added in a percentage range from two percent to six percent at one percent intervals, and no increase in the explosive energy was obtained and no change was produced in the curve shown in the drawing.

The explosive of this invention may take various forms, such as a shaped charge, a pressed booster, pellets, sticks, or in containers. The pellets are made in the conventional way by pressure dies, and such pellets may be used in bombs or similar applications. The explosive of this invention when in stick form may be detonated with a blasting cap of conventional construction which is inserted into a preformed hole in the explosive. Also, when the explosive of this invention is disposed in a container, a prima cord may be used for detonating same, such as in mining applications.

The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape, and materials as well as in the details of the illustrated construction may be made without departing from the spirit of the invention.

We claim:

1. A non-aqueous cap-sensitive explosive consisting essentially of:

(a) gelled nitromethane in an amount from about ten percent to about thirty percent by weight;

(b) a nitrate in an amount from about ninety percent to about seventy percent by weight;

(c) said nitrate being selected from the group consisting of ammonium nitrate, sodium nitrate, lithium nitrate, and mixtures of two or more of said nitrates; and

(d) said nitromethane being essentially the only nitroparaffin present in said explosive.

2. The explosive set forth in claim 1, wherein:

(a) the particle size of said nitrate is from about 500 microns to about one-eighth of an inch.

References Cited UNITED STATES PATENTS 2,712,989 7/1955 Maisner 149-90 X 2,891,852 6/1959 Schaad 149-89 3,035,948 5/1962 Fox 149-90 X 3,035,950 5/1962 Long 149-89 X 3,181,982 5/1965 Burnside et al. 149-19 3,242,022 3/1966 Atkins et a1. 149-89 3,318,741 5/1967 Jones 149-89 3,338,165 8/1967 Minnick 149-89 X 3,377,217 4/1968 Francis 149-89 X 3,379,586 4/1968 Francis 149-19 3,377,218 4/1968 Brown 149-89 X 3,356,544 12/1967 Fee et a1 149-89 X 3,419,444 12/1968 Minnick 149-89 X CARL D. QUARFORTH, Primary Examiner S. J. LECHERT, Assistant Examiner U.S. Cl. X.R.