US2388368A - Ignition composition - Google Patents

Description

- lose its sensitivity to low temperature ignition as atent'ed Nov. 6, 3.45

Guy F. Rolland, McKeansbui-g, Pa, assignor to Atlas Powder Company, Wilmington, DeL, a corporation of Delaware No Drawing. Application May 6, 1941, Serial No. 392,183

- 9 filaims.

This invention relates to improved ignition compositions, and more particularly to the improvement of ignition compositions which comprise a metallic acetylide and to a method of improving the stability and reliability of metallic acetylide ignition compositions. 'It has for its main object the improvement of the inflammability, stability and reliability of such ignition compositions after prolonged storage periods. Other objects will also be evident from the following description of my invention.

Ignition compositions comprising an inflammable metallic acetylide such as, for example, cuprous acetylide, mercury acetylide and silver acetylide are useful for many purposes and particularly where the ignition composition is to be ignited by. electrical means, such as, for example, electrically heated bridge wires, spark gaps, etc. They are adaptable and greatly valued for use, for example,-in electric detonators, electric squibs, electric starter cartridges, electrically fired coal blasting devices, oil-well casing'perforators, etc., as is well known. For such purposes, cuprous acetylide in particular is highly desirable because it is readily ignited by means of a relatively small amount of heat and burns with a quick but relatively non-violent flash. One objection to cuprous acetylide has always existed, however, in that it has had a tendency to well as its desirable flash characteristics, after prolonged storage periods and particularly when stored under conditions involving elevated temperatures. The rate of deterioration of cuprous acetylide, under fixed storage conditions, has varied widely among diiierent manufactured lots of the materials, some lotseven showing a marked decrease in sensitivity with as little as three months storage at a temperature of 50 C. while other lots show little or no deterioration over much longer periods under the same storage conditions.

The lots which exhibit marked decrease in sensitivity, as evidenced, for example, by their decreased sensitivity to ignition by the heated bridge wire of an electric match, are unsuitable for use as ignition compositions. Consequently, it is necessary, before a lot or cuprous acetylide ismade into matches or the like, to store it for extensive periods, as, for example, from two to three months, in order to determine whether or notit has the undesirable characteristic of reduction in sensitivity. with aging.

Now, in accordance with the present invention,

I overcome this objection by greatly prolonging 55 the inflammation-sensitivity life of the metallic acetylide by associating with it a stabilizer comprising abietic acid. A typical example of such a stabilizer is rosin, as obtained, for example, from the distillation of turpentine oil from crude turpentine, which product I have found to be very eflective in improving the storage life of metallic acetylide types of ignition compositions, when intimately associated therewith, even in very small proportions.

It is customary to apply the acetylide, such as, for example, cuprous acetylide, to the bridge wire or other heat-producing means in the form of a suspension in nitrocellulose lacquer. A commonly used solvent for such lacquer is amyl acetate, although other suitable solvents may be employed. Also, the lacquer may comprise binders other than nitrocellulose. The stabilizer (abietic acid or composition comprisin this material) may be conveniently dissolved in the lacquer, in which the acetylide is to be suspended. The stabilizer may also be added to the acetylide-lacquer mixture in the form of an amyl acetate solution. Either method of application insures an intimate mixture of the acetylide and abietic acid stabilizer when the solvent ha evaporated from the mixture. After the lacquer mixture has been applied to a bridge wire, for example, (usually by dipping the device into the mixture), the lacquer solvent is allowed to evaporate, resulting in the formation of a coherent bead of heat sensitive .composition about the bridge wire or other heat producing device. The electricignition device may then be completed in any manner desired, as by successive applications of protecting lacquer, by applying an auxiliary flame-producing mixture which may consist, for example, of a mixture of. charcoal and potassium chlorate suspended in lacquer, etc., the solvent being allowed to evaporate between each application of material to the assembly. Wellknown devices of this type are known as fuseheads or match-heads.

A non-limiting example of, an ignition composition or the present invention is as follows:

Cuprou acetylide grams Rosin, grade N 1.92 grams-dissolvedin 10 ml. amyl acetate Nitrocellulose lacquer (1 oz. per gallon) 63.5 ml.

may be employed with good efiect. Also, larger amounts may be employed, although it is desirable not to replace too much of the cuprous acetylide with rosin, since the cuprous acetylide is the active inflammable ingredient of the ignition composition. Generally, I have found that amounts of'rosin up to 5% will have no materially adverse effect on the firing characteristics'of the acetylide composition. In general, therefore, the stabilizer of the composition of the present invention is present'in amounts small enough to be effective in increasing the stability of the inflammable metallic acetylide without adversely affecting the firing characteristics of the acetylide. The amount of lacquer used may vary considercuprous acetylide used. The actual-amount used is such as to obtain proper consistency for application to the bridge wire. The grade or rosin used need not be that indicated above but may be any of the other grades of rosin, as well as pure abietic acid.

Sensitivity of ignition comositions on matched eads As manu- After 3 mos. factured at 50 C.

Cuprous acetylide stabilized with Ma. Ma.

grade N rosin 270 275 Cuprous acetylide with no stabilizer" 260 305 The sensitivity of the ignition composition on the match heads was determined by measuring the minimum amount of current through the bridge wire required to cause consistent ignition of the composition. The higher minimum current requirement in the above tabulation indicates a lower sensitivity. The increase invcurrent requirement of the unstabilized cuprous acetylide indicates that deterioration had already begun, whereas the current requirements for the stabilized material was identical, within experimental limits of error, after the storage period, indicating continued good sensitivity.

It will therefore be evident, that by means of the present invention, I provide not only greater storage life to ignition compositions comprising .inflammable metallic acetylide, resulting in a more uniformly low minimum firing current therein, and thereby greatly increasing the functioning reliability .aiter storage, but I also provide a means of maintaining a more uniform minimum firing current from batch to batch of inflammable metallic acetylide, irrespective of its age. This latter feature serves to insure better series firing characteristics and particularly where ignition devices of various ages are connested in the same series circuit.

It is to be understood that the ignition compositions of the present invention may comprise ably depending on the character of the particular ingredients other than those mentioned above, as, for example, fuels, oxidizers, etc., without departing from the present invention.

The above example and test results are cited merely for purposes of fully illustrating the invention and are not to be considered as limiting. Having described my invention, what I claim is" v 1. An ignition composition comprising amixture of a metallic acetylide and a stabilizer comprising abietic acid.

2. An ignition composition comprising a mixture of cuprous acetylide and a stabilizer comprising abietic acid.

3. An ignition composition comprising a mixture of a metallic acetylide and a stabilizer consisting essentially of rosin.

4. An ignition composition comprisin a mixture of cuprous acetylide and a stabilizer consisting essentially of rosin.

5. In an electric ignition device, an electrically heated bridge wire in direct contact with an inflammable ignition composition comprising a mixture of cuprous acetylide and a stabilizer comprising abietic acid. 1

6. In an electric ignition device, an electric I spark gap having within the gap and adapted to become ignited by a spark passing through the gap, an inflammable ignition composition comprising a mixture of cuprous acetylide and a stabilizer comprising abietlcacid.

{7. In combination in an ignition device an inflammable ignition composition comprising a mixture of a metallic acetylide and a stabilizer comprising abietic acid, and a heat-producing means positioned to ignite said composition.

8. In combination in an ignition device an inflammable ignition composition comprising a mixture of cuprous acetylide and a stabilizer comprising abietic acid, and a heat-producing means positioned to ignite said composition.

9. An ignition composition comprising a mixture of a a metallic acetylide, a stabilizer comprising abietlc acid, and a binder.

. GUY F. ROLLAND.