US3634155A

US3634155A - Priming composition

Info

Publication number: US3634155A
Application number: US836159A
Authority: US
Inventors: Josef Prior; Aloys Florin
Original assignee: Dynamit Nobel AG
Current assignee: Dynamit Nobel AG
Priority date: 1968-06-29
Filing date: 1969-06-24
Publication date: 1972-01-11
Anticipated expiration: 1989-01-11
Also published as: DE1771720A1; DE1771720B2; GB1252816A; NO125847B; FR2014445A1

Abstract

Granulated initiator explosive composition having a weight ratio of 5:95 to 95:5 of lead azide to lead trinitroresorcinate and 0.1 to 0.5 weight percent binder calculated on total weight of the composition.

Description

Unite States aient Inventors Josef Prior [56] References Cited UNITED STATES PATENTS 2,295,104 9/1942 Garfield 149/26 X 2,421,778 6/1947 Fleischer et al... 149/26 2,464,777 3/1949 Rubenstein et a1. 149/26 X 3,291,663 12/1966 Taylor et a1 149/26 X FOREIGN PATENTS 156,429 1/1921 Great Britain 149/26 Primary Examiner Leland A. Sebastian Attorney-Burgess, Dinklage & Sprung ABSTRACT: Granulated initiator explosive composition having a weight ratio of 5:95 to 95:5 of lead azide to lead trinitroresorcinate and 0.1 to 0.5 weight percent binder calculated on total weight of the composition.

PRlMllNG COMPGSITION This invention relates to explosive compositions. lt more particularly refers to a novel explosive composition and form useful as an initiator.

Mixtures of lead azide with lead trinitroresorcinate have been used for a long time as initiators for detonating caps. These mixtures have, besides the considerable advantage which the extraordinary ignition sensitivity of the lead trinitroresorcinate imparts to the mixture, also disadvantages as compared to using lead azide by itself. For example, it is extremely difficult to obtain homogeneous mixtures of both these substances by plain mixing, and therefore in prior art it was always expected that separations would occur.

While separations towards an increased proportion of lead azide are not so critical because smaller amounts of lead trinitroresorcinate still provide the mixture with a sufficient ignitibility, a decrease of lead azide is feared in practice because the initiator force of the mixture, which is based alone upon the proportion of lead azide, becomes considerably weakened so that ignition failures may occur. In practice, this potential problem is compensated for by using a considerably higher amount above the required amount of priming mixture.

It is an object of this invention to provide an improved initiator.

Other and additional objects of this invention will become apparent from a consideration of this entire specification including the claims.

These objects can be achieved by using, in accordance with the invention, a mixture, as a priming composition, of lead azide and lead trinitroresorcinate granulated in the wet state with binders. It is preferred that the ratio of lead trinitroresorcinate to lead azide is about 5:95 to 95:5 weight percent with about 0.1 to 0.5 weight percent binder referred to the total weight. Because of the high sensitiveness to percussion and shock of a mixture of lead azide and lead trinitroresorcinate, the prior art did not consider production of such a mixture in granulated form.

Suitable for use as binders are nitrocellulose, methyl-, ethylacetylor similar cellulose derivatives or alginates, guar flower and high polymers which are water-soluble or capable of swelling with water such as polyvinyl alcohols, polykylene glycols (ethers) or polyvinyl pyrrolidenes. We would particularly like to mention nitrocellulose with a nitrogen content of l2to 14 percent and acetone-soluble acetyl cellulose. The lead trinitroresorcinate particle sizes can vary from coarse to fine. The distribution of components in the particles is better in fine particle sizes. The lead azide can be added in difierent percentages, Le, 88 percent 90 percent, 92 percent, 94 percent, and 98 percent.

The granulating of the lead azide trinitroresorcinate mixtures can take place by precipitation of the binder from a solution (l) or by machine granulating or by hand.

(I) GRANULATING BY PRECIPITATING THE BINDER FROM A SOLUTION In a l liter kettle with stirrer (about 150 rpm, there are added 30 liters of acetone and 300 g. of nitrocellulose are dissolved therein. When the nitrocellulose has become completely dissolved, there are added 7 kg. of PbN and 3 kg. of lead trinitroresorcinate (in any sequence). After adjusting the temperature to about 20 C., about 50 liters of H 0 of the same temperature are permitted to run into the mixture within 30 minutes.

After the addition of the H 0, a post-stirring for an additional 2 minutes is carried out. Thereafter, the formed cake is filtered off by suction, washed with alcohol, and then dried at an air temperature of 40 to 50 C. The dry product forms into readily flowable granules, which may be separated by sifting into the desired granular size fractions.

The mixtures obtained in accordance with the described granulating method are characterized by excellent resistance to separation. I t

Thus, 100 g. of the mixture obtained in accordance with method (I) were loaded into a conventional loading device which was vibrated at a predetermined vibration with the aid of a vibration generator. The analysis showed a substantially constant ratio of the components in the mixture from the beginning to the end of the loading process.

By way of comparison, there was loaded in the same apparatus the same mixture of components without binder, i.e., in nongranulated form. The mixture proportions at the beginning of the loading were relatively homogeneous, yet at the end of the loading procedure visible nonhomogeneity, which could be seen by the nests of the lead trinitroresorcinate in the yellowish-white lead azide, appeared and very difierent proportions of components which ranged up to a mixture ratio of 1:1 leadazide/ leadtrinitroresorcinate.

The priming force of this mixture is now only at 50 percent of the mixture of 70 percent lead azide and 30 percent lead trinitroresorcinate.

A further advantage of the priming composition in accordance with the invention is the fact that the same may be produced in large charges. Furthermore, the mixture which constitutes the initial primer is readily flowable. The impact and friction sensitivity is strongly diminished without having appreciably reduced the ignition sensitivity or priming limit.

We claim:

1. Method for the production of explosive initiator compositions comprising free-flowing granules of about 5 to weight percent lead azide, about 5 to 95 weight percent lead trinitroresorcinate and a binder; which method comprises forming a fluid form mixture of lead azide, lead trinitroresorcinate, a cellulose ester and a solvent for said cellulose ester; adding a nonsolvent liquid to said mixture in an amount and at a temperature sufficient to precipitate said lead azide, said lead trinitroresorcinate and said cellulose ester from said fluid form mixture; removing substantially all of the liquid from said precipitate; and recovering free-flowing granules of lead azide and lead trinitroresorcinate in the proportions specified above which granules are bonded by said cellulose ester.

2. Method as claimed in claim 1 wherein said cellulose ester is a member selected from the group consisting of nitrocellulose, acetone soluble acetyl cellulose, methyl cellulose and ethyl cellulose.

3. Method as claimed in claim 1 wherein said solvent is acetone and said precipitant is water.

4. Method as claimed in claim 1 wherein said cellulose derivative is present in said admixture in a proportion of about 0.1 to 0.5 weight percent.

Claims

2. Method as claimed in claim 1 wherein said cellulose ester is a member selected from the group consisting of nitrocellulose, acetone soluble acetyl cellulose, methyl cellulose and ethyl cellulose.
3. Method as claimed in claim 1 wherein said solvent is acetone and said precipitant is water.
4. Method as claimed in claim 1 wherein said cellulose derivative is present in said admixture in a proportion of about 0.1 to 0.5 weight percent.