US2711948A - Blasting explosive and process for producing same - Google Patents

Description

BLASTING EXPLGSIXE AND PROCESS FOR PRODUCING SAME George P. Sillitto, West Kilbride, and Alexander Butchart, Ardrossan, Scotland, assignors to Imperial Chemical Industries Limited, a corporation of Great Britain N Drawing. Application August 27, 1951, Serial No. 243,908

Claims priority, application Great Britain September 12, 1950 Claims. (Cl. 527) The present invention relates to an improvement in blasting explosives of the kind comprising fibrous ungelatinised nitrocellulose and an oxidising salt.

The object of the present invention is to eliminate nitrocellulose dust and possibility of ignition by accidental electrostatic charges in the production of the aforesaid blasting explosives.

According to the present invention the process for the production of blasting explosives of the kind comprising fibrous ungelatinised nitrocellulose and an oxidising salt comprises mechanically mixing the ungelatinised fibrous nitrocellulose in water wet condition with the oxidising salt, including in the mixture comprising nitrocellulose and oxidising salt 2 to glycerine on the total Weight of the water-free composition, and removing the water from the resulting glycerine containing mixture.

It has been found that after removing the water from the glycerine containing mixture 2% glycerine on the water-free blasting explosive is usually sufficient for the product to be glycerine-moist while a quantity of glycerine in excess of 10% reduces the sensitivity of the water-free glycerine-moist product to an undesirable degree.

The blasting explosives produced according to the process of the present invention may include additional constituents to the nitrocellulose and oxidising salt and these additional constituents may be mixed with the oxidising salt before it is mixed with the nitrocellulose in water-wet condition.

If desired the glycerine may be in solution in the water with which the nitrocellulose is associated when it is introduced into the mixing operation, but in general it is more convenient that the water-wet nitrocellulose should consist of nitrocellulose and water only and that the glycerine should be introduced subsequently either before or along with the other ingredients of the composition.

The presence of the water in the mechanical mixing operation renders it safe, and after the explosive has been dried oif for instance at a temperature of 50 to 60 C., the glycerine left in association with the nitrocellulose renders it free from the hazard characteristic of explosives containing dry ungelatinised nitrocellulose particles.

It will be understood that the fibrous ungelatinised nitrocellulose, which constitutes the principal explosive sensitising ingredient of the composition, is itself an oxidisable ingredient and that the glycerine also constitutes an oxidisable ingredient in the composition, and that the explosive should contain suflicient quantity of the oxidising salt to render it substantially free from oxygen deficiency or even to confer upon it a slight oxygen surplus. For economic reasons however it is desirable that the composition should contain a high proportion of an explosive salt less costly than the fibrous nitrocellulose, for instance ammonium nitrate, which has both the character of an oxidising salt and of an 2,711,948 Patented June 28, 1955 explosive salt. The minimum proportion of fibrous ungelatinised nitrocellulose required to confer the neces- Example Parts Water-wet pulped fibrous mixture of industrial nitrocelluloses and guncottons, of average nitrogen content approximately 12.5%, and containing 8 parts water and 21 parts dry weight of nitrocellulose 26 Ammonium nitrate 75.5 Glycerine 3 Oleic a id 0.5

The glycerine and the oleic acid are first added to the water-wet pulped fibrous nitrocellulose mixture and the ammonium nitrate is then mixed in with the wet material in a mixer until the ingredients are well distributed, said mixer being one that provides for thorough mixing. During this process the ammonium nitrate becomes partly liquefied by the water present. The resulting damp material is dried 01f in an oven at 55 to 60 C. When dry the powdery material is cartn'dged in pre-formed waxed paper cases of 1% inch diameter in known manner and the open ends of the cases are folded in and waxed. The oxygen surplus of the composition over that required for complete combustion of the carbon and hydrogen is 1.6 grams oxygen per grams and the power as determined by the ballistic mortar is 81% of that of blasting gelatine. The detonation of the explosive is easily initiated by a No. 6 commercial lead azide/tetryl detonator having an aluminum casing and the velocity of detonation as measured by the Dautriche method is 2700 metres per second. In a gap test in which two cartridges of 1% inch diameter held in line at varying distances apart by an outer paper layer are tested, one of the cartridges having a detonator inserted into the end remote from the gap between the two cartridges, it is found that the cartridge without the detonator detonates when the distance between the two cartridges is 1 inch, but fails to detonate when it is 3 inches. This explosive is suitable for application in quarrying in reasonably dry situations. During the mixing of the ingredients of the composition and subsequently drying and cartridging operations, no airborne particles of dry nitrocellulose are observed in the vicinity of the operation.

What we claim is:

l. A process for the production of blasting explosives of the kind comprising fibrous ungelatinised nitrocellulose and an oxidising salt which comprises mechanically mixing ungelatinised fibrous nitrocellulose in water-wet condition with the oxidising salt, including in the mixing comprising nitrocellulose and oxidising salt 2 to 10% glycerine on the total weight of the water-free composition, and removing the water from the resulting glycerine containing mixture.

2. A process as claimed in claim 1 wherein additional constituents to the nitrocellulose and oxidising salt are incorporated during the mechanical mixing.

3. A process as claimed in claim 2 wherein the said additional constituents are mixed with the oxidising salt before it is mixed with the nitrocellulose in waterwct condition.

4. A process as claimed in claim 1 wherein the glycerine is introduced after the ungelatinised fibrous nitrocellulose in water-wet condition has been mechanically mixed 'with the oxidising salt.

Q 5. A blasting explosive composition comprising fibrous ungelatinised nitrocellulose, an oxidising salt and from 2% to 10% of glycerine on the total weight of Water-free composition.

References Cited in the file of this patent UNITED STATES PATENTS 1,627,692 Dupont et al. May 10, 1927 4 1,728,307 Rupp Sept. 17, 1929 1,780,911 Du Pont Nov. 11, 1930 2,554,179 Fordharn May 22, 1951 OTHER REFERENCES Uses and Applications of Chemicals and Related Materials by Thomas C. Gregory, published by Reinhold Publishing Co., New York, 1939, pages 300, 301, 302. (Copy in Library.)

Claims (2)

1. A PROCESS FOR THE PRODUCTION OF BLASTING EXPLOSIVES OF THE KIND COMPRISING FIBROUS UNGELATINISED NITROCELLULOSE AND AN OXIDISING SALT WHICH COMPRISES MECHANICALLY MIXING UNGELATINISED FIBROUS NITROCELLULOSE IN WATER-WET CONDITION WITH THE OXIDISING SALT, INCLUDING IN THE MIXING COMPRISING NITROCELLULOSE AND OXIDISING SALT 2 TO 10% GLYCERINE ON THE TOTAL WEIGHT OF THE WATER-FREE COMPOSITION, AND REMOVING THE WATER FROM THE RESULTING GLYCERINE CONTAINING MIXTURE.

5. A BLASTING EXPLOSIVE COMPOSITON COMPRISING FIBROUS UNGELATINISED NITROCELLULOSE, AN OXIDISING SALT AND FROM 2% TO 10% OF GLYCERINE ON THE TOTAL WEIGHT OF WATER-FREE COMPOSITION.