US2268372A - Ignition composition comprising pyro-lead salt-chlorate - Google Patents

Description

Patented Dec. 30, 1941 I CROSS REFERENCE IGNITION COMPOSITION COMPRISING PYEO-LEAD SALT-CHLORATE Lawton A. Burrows, Woodbury, and George A. Noddln, Wenonah, N. 1., assignors to E. I. du Pont de Nemonrs & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application September 30, 1939,

Serial No. 297,272

' 8 Claims.

blasting caps used in the initiation of explosive charges, particularly in electric blasting caps, as well as in other devices where a small charge of a defiagrating explosive is ignited by means of an electric current.

A particular field for such composition is as a loose ignition top charge in an electric blasting cap. It is essential here that the composition becapable of ready ignition on application of the heat from the passage of an electric current through a fine, highly-resistant wire in contact with the loose material. Ignition must not only be certain but it must take place with the use of a low firing current. The composition must also be sufiiciently stable so that its ability to ignite will be uniform and unaffected by storage, even under unfavorable conditions. On the other hand, such a composition must not be unduly sensitive, such, for example, that it will be fired by small electrostatic discharges or be sensitive to slight Jars and shocks. It must likewise give off sumcient flame and heat on ignition to bring about the firing of an adjacent explosive charge.

. tory.

The object of the present invention is an improved ignition composition. A further object is an ignition composition possessing favorable firing characteristics and having the ability to ignite an adjacent explosive charge from its combustion flame. A still further object is an ignition composition which is satisfactory as a loose top charge in an electric blasting cap. Additional objects will be disclosed as the invention is described more'fully hereinafter.

We have found that the foregoing objects are accomplished by employing as an ignition composition smokeless powder in finely divided con-, dition, together with a lead salt of a nitrophenol. The lead salts of various nitrophenols are adaptplex or double salt of lead nitrate with a lead salt of a nitrophenol, particularly the double salt of lead nitrate with 4,6-dinitro-ortho-cresol, which may be designated more exactly at 3,5-dinitro-2-hydroxy-1-methyl benzene, as is dis-. cussed more at length in the Burrows and Filbert application, Serial No. 171,512, filed October 28, 1937.

We find it desirable, furthermore, to include an oxidizing agent in the ignition composition, in addition to the comminuted smokeless powder and the above complex lead salt of a nitrophenol. Asthe preferred oxidizing agent we employ potassium chlorate.

As examples of specific embodiments of our invention, we may cite the following:

Example 1 basic lead salt of 4,6-dinitro-orth'o-cresol, and

potassium chlorate, respectively, was grained ed for use in the above manner, for example,

the salts of dinitrophenol, trinitrophenol, dinitrocresol, and the like. A lead salt of dinitroortho-cresol is our preferred salt for use. More specifically, we find it desirable to employ a com- -above loose charge was 0.299 ampere.

with a suitable solution, dried, and screened. The firing current required for ignition of the The charge consistently failed to give detonations when a A" steel balllwas dropped upon a layer of it from a height of 10". The composition'had satisfactory ignition ability when fired in the presence of other explosive charges.

Example 2 Amblendwas prepared comprising a. grained mixture of '75 parts of comminuted pyro smokeless powder and 25 parts of a double salt of lead nitrate with a his basic lead salt of 4,6-dinitroortho-cresol. After drying and screening, the composition possessed a minimum firing current requirement of 0.309 ampere. tion failed consistently to fire when the steel ball of Example 1 was dropped on a layer thereof from-a height of 40". The composition was like- SEARCH Room The composiwise satisfactory in the absence of susceptibility to electrostatic charges.

The compositions of the type illustrated in the foregoing examples are particularly adapted for use as loose ignition charges in electricblasting caps. Preferably, we use compositions within the range of 50-75% of pyro smokeless powder. l-25% potassium chlorate, and -25% of the complex salt of lead nitrate with dinitro-orthocresol. If no inorganic oxidizing agent is included, a desirable range of compositions will be 75-85% pyro powderand 25-15% of the lead double salt. We find such compositions of particular importance as top charges in; electric blasting caps containing lead azide as the primary detonating explosive, the azide being superposed on a base charge of tetryl or other suitable material. The composition will be particularly useful in electric blasting caps of the bridge plug type, where a loose ignition charge surrounds the bridge wire connecting the two leg wire terminals below the plug. The preferred compositions are uniform in rate of burning, but sufliciently slow to be satisfactory in series firing.

It has been stated that one of the principal ingredients of the composition is ground smokeless powder. The grade known as pyro powder will be the one preferably used, which signifies the grade made from nitrocellulose substantially soluble in a mixture of 2 parts by volume of ether to 1 part of ethyl alcohol, and having a nitrogen content of about 12.6%.

The lead salt used may be such a salt of any of the nitrophenols, but preferably will be a complex salt of lead nitrate with the lead salt of 4,6-dinitro-ortho-cresol. Our preferred salt may be designated as lead nitrate-bis basic lead-4,6- dinitro-ortho-cresylate monohydrate, and has the following formula:

As stated, we find it desirable, though notessential, to include an inorganic oxidizing agent as an ingredient of our ignition composition. I

Potassium chlorate is the preferred salt for such use because of its uniform performance. Other inorganic oxidizing salts may be used in its place. however, such as various nitrates, chlorates, perchlorates, and the like.

Our ignition composition has been designed particularly for use as a top charge in electric blasting caps. It will be capable of application in other fields, however, where similar properties are advantageous; for example, it may be used in ordinary blasting caps, delay caps, electric squibs, flashlight compositions, electric fuses employing an ignitable composition, and elsewhere.

We have described our invention at length in the foregoing, but it will be understood that many variations may be made in exact compositions without departure from the spirit of the invention. We wish to be limited therefore by the following patent claims:

We claim:

1. In a blasting initiator, an ignition composition consisting essentially of a loose charge of comminuted colloided smokeless powder and a lead salt of a nitrophenol.

2. In a blasting initiator, the composition of claim 1, in which the nitrophenol is dinitrophenol.

3. In a blasting initiator, the composition of claim 1, in which the nitrophenol is a dinitrocresol.

4. In a blasting initiator, an ignition composition consisting essentially of 'comminuted colloided smokeless powder and a complex salt of lead nitrate with a his basic lead salt of 4,6-dinitro-ortho-cresol.

5. In a blasting initiator, an ignition composition consisting essentially of -85% of comminuted colloided smokeless powder and 25-15% of a complex salt of lead nitrate with a his basic lead salt of 4,fi-dinitro-ortho-cresol.

6. In a blasting initiator, an ignition composition consisting essentially of comminuted colloided smokeless powder, an inorganic oxidizing agent, and a lead salt of a nitrophenol.

7. In a blasting initiator, an ignition composition consisting essentially of comminuted colloided pyro nitrocellulose, potassium chlorate, and a complex salt of lead nitrate with a his basic lea-d salt of 4,6-dinitro-ortho-cresol.

8. In a blasting initiator, an ignition composition as the top charge in an electric blasting cap, said composition consisting essentially of 50-75% of colloided pyro nitrocellulose, 125% of potassium chlorate, and 15-25% of a his basic lead salt of 4,6-dinitro-ortho-cresol.

LAWTON A. BURROWS. GEORGE A. NODDIN.