US1965731A - Explosive composition - Google Patents

Description

' Patented July 10,1934

PATENT- OFFICE EXPLO SIVE COIVIPOSITION Clifford A. Woodbnry, Media, Pa., assignor to E. I. dnPont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application March 8, 1933,

Serial No. 659,503 (61. 52-13) My invention relates to new dynamite explosives of the gelatinous-type, and more particularly to that class of explosives commonly designated as blasting ,gelatins.

This application is a continuation in part of my co-pending application Serial No. 539,631, filed May 23, 1931.

There have been in common use two types o f blasting gelatinous explosives, namely, gelatin m dynamite and blasting gelatin.

Gelatin dynamite is made by gelatinizing nitroglycerin with a relatively small amount of nitrocotton and then mixing into the semi-liquid gel various absorbents and oxidizing salts. This explosive is not as strong as nitroglycerin and is not as tough and rubbery as blasting gelatin so that it can'be readily filled into paper cartridges by means of machines designed for that purpose. The highest strength gelatin dynamite is about 90% as strong as nitroglycerin and contains a,

mam'mum of around 83% nitroglycerin. An example of 90% gelatin dynamite is as follows:

90% gelatin dynamite Nitroglycerin 80.5 to 83.0 Nitroco 3.5 to 4.5

Blasting gelatin is a colloidal solution of nitrocellulose in nitroglycerim'usually containing no other ingredients except a small amount of acid acceptor. It is essentially 100% as'strong as nitroglycerin, contains no oxidizing salts and 5 is of a tough and rubbery consistency which does not lend itself to being cartridged on the machines commonly employed for gelatin dynamite. Therefore, it is necessary to extrude blasting gelatin, cutit into the lengths desired and 40. wrap itwith paper by hand.

The usual compositionof blasting gelatin is 90 to 92 per cent. of nitroglycerin, 6 to 8 per cent. of nitrocellulose and about 1 per cent. of an acid acceptor, such as calciumicarbonate.

In the manufacture of blasting gelatin, nitrocellulose is commonly dissolved in nitroglycerin to form the colloidal gel. Sufflcient nitrocellulose is used so that a solid plastic material is obtained.

One of the large uses of blasting gelatin at the present time is in shooting oil wells. When used in this type of work the explosive is lowered to great depths underground in the oil wells. These depths may be as much-as several thousand feet,, 55 and the explosive is frequently exposed to the action of water and to considerable pressure. Under such conditions, it is highly important that the explosive be sufficiently sensitive so that detonation is-assured, but yet not so sensitive as to make it unsafe for handling. I

Blasting gelatin, as customarily made, is quite sensitive at the time of manufacture. It frequently becomes less sensitive on aging, especially under conditions that are met in oil-wells, where the explosive must often remain for a consider- 6 able period between the time of loading and of shooting. While some improvements in this respect have been brought about by the use of explosive oils of different properties and consistencies, such means have not given wholly satisfactory results.

I have discovered that an improved type of blasting gelatin for use in oil wells and the like is obtained, if a relatively small percentage of a solid, non-gelatinizing absorbent ingredient, preferably of a low-density character is incorporated with the usual ingredients of blasting gelatin. The-greatest benefit of 'these absorbents is obtained when they are introduced in place of the nitrocellulose. .While various absorbents such as kieselguhr, puffed or flaked cereal products, bagasse pith and those obtained from wood, such as ordinary wood or balsa wood pulp, may be used to bring about desirable improvements, I find wood pulp very well adapted 35 for this purpose. These ingredients may be addedwith the nitroglycerin and the nitrocellulose at the beginning of the gelatinization, or a prelinrinary gelatinization of the nitroglycerin may be brought about, prior to the addition of the wood pulp, or the like.

The proportions of nitroglycerin, nitrocellulose and absorbent ingredients may, of course, be varied in composition within rather wide limits. It is essential, however, that sufficient nit'rocellulose be used to secure thorough gelatinization, so that the blasting gelatin obtained will have the proper elastic, rubbery consistency for satisfactory use.- In the blasting gelatins as com .monly manufactured, the liquid explosive and the loo nitrocellulose may be used in the approximate proportion of 91 to 8: I have found that a satisfactory composition is obtained by replacing the nitrocellulose with a small percentage of wood pulp or other absorbent material. While various materials maybe used for such replacement, it v is essential that it be a material having no gela- -tinizing eifect on nitroglycerin and substantially insoluble therein. This absorbent material may and 10.0. However, I prefer to use between 3 and 6 per cent.

In order to illustrate one embodiment of my invention more clearly, the following example is given of a blasting gelatin according to my invention:

It will be noted that the sensitiveness is greatly increased by the replacement of a portion of the nitrocotton with wood pulp. In the case of blasting gelatin,'if a 1 /1 x 8" cartridge is cut in half, separated, and one-half the cartridge fired bymeans of acap, the second half will als0 detonate provided the distance between the two-halves is not over 8". In the case of my modified blasting gelatin, this distance is increased to 18". The velocity and strength are the same in both explosives. The TNT strength value is the grams of TNT equal in strength to 10 grams of explosive.

My modified blasting gelatin is 100% as strong as nitroglycerin. The usual blasting gelatin becomes insensitive if stored for. any appreciable length of time while my modified blasting gelatin retains good sensitiveness on long storage. It contains a minimum of approximately 88% nitroglycerin. It can be punched in the. gelatin cartridge machines in large sizes but usually does not work very well in the machine insmall diameter cartridges.

There are certain critical limits in the proportions used in the manufacture of the three types of gelatins. It is difficult to formulate a gelatin dynamite much stronger than as there is little room left in the formula for introducing oxidizing salts and adjusting the composition for oxygen balance and working qualities. Probably about 86% nitroglycerin is the maximum percentage which can be successfully used in formulating a gelatin dynamite. In the case of my modified blasting gelatin, a minimum of at least about 88% nitroglycerin is necessary in order to have strength and the consistency required for the blasting gelatin type of explosive. Preferably the nitroglycerin content of the blasting gelatin is not less than 90%. One reason that it is possible to make an explosive of essentially 100% strength with only 88% of nitroglycerin is due to the fact that in my modified blasting gelatin the introduction of pulp causes a greater deficiency in oxygen. Tests have proved that the maximum strength is obtained when the oxygen balance is about minus 10, that is, 100 grams of explosive would require 10 grams additional oxygen in order to yield fully oxidized products. Therefore, while it is within the scope of my invention to introduce oxidizing salts such as nitrate of soda into this nee -731 modified blasting gelatin, it would not be preferable to doso because of the adverse eflect such salts would have on the strength of the product.

In the foregoing description of my invention, the term nitroglycerin has been usedto designate the explosive oil. It should be understood that by the term nitroglycerin is meant either this compound by itself or with the addition 'or partial substitution of any of the commonly used. freezing point depressants such, for example, as ethylene glycol dinitrate, nitrated polymerized glycerin, nitrated sugars, nitrated chlorhydrins, etc.

A blasting gelatin made according to my invention has several advantages over the compositions previously in use. A particular advantage is that the sensitiveness of the blasting gelatin to the propagation .of the explosive wave is increased, with no sacrifice of strength, velocity, or resistance to water. Moreover,- a blasting gelatin-of the above description .does not have the tendency to become insensitive with age and under, the effect of water pressure, such as is met in the case of blasting gelatins heretofore described.

As many apparently widely different embodiments of this invention may be made without departing from the spirit thereof, it is to be understood that I'do not limit myself to the foregoing examples or descriptions, except as indicated in the following patent claims.

I claim:

1. A modified blasting gelatin comprising about 90%' of a liquid explosive ingredient in which sufiicient of the nitrocellulose has been replaced by an absorbent material insoluble in nitroglycerin to give an amount of nitrocellulose not exceeding 5% of the weight of blasting gelatin.

2. The product of claim 1 in which the absorbent material is taken from a group consisting of carbonaceous combustible materials and inert absorbents.

3. The product of claim 1 in which the absorbent material is taken from a group of carbonaceous combustible ingredients of the nature of fibrous organic bodies."

4. A modified blasting. gelatin containing at least 88% of a liquid explosive, a solid, non-gelatinizing absorbent ingredient substantially insoluble in nitroglycerin, and an amount of nitrocellulose not exceeding 5% of the weight of blasting gelatin.

51 The product of claim 4 in which the solid, non-gelatinizing ingredient is wood pulp.

6. The product of claim4 in which the solid, non-gelatinizing ingredient is a carbonaceous material.

'7. The product of claim .4 in which the solid, non-gelatinizing ingredient is bagasse pith.

8. A modified blasting gelatin containing about 90% liquid explosive ingredient in which a considerable portion of the nitrocellulose has been replaced by a. fibrous, carbonaceous absorbent ingredient, substantially insoluble in nitroglycerin."

,9. .A modified blasting gelatin containing not less than 88 to 92% of a liquid explosive ingredient and from 0.5 to 9.4% of a fibrous, carbonaceous absorbent ingredient, substantially insoluble in nitroglycerin.

10. A modified blasting gelatin containing not less than 88 to 92% of a liquid explosive ingredient and from 0.5 to 9.4% of a low density fibrous absorbent material.

90 to 92% of nitroglycerin, nitrocellulose and from 3 to 6% of a fibrous, carbonaceous absorbent ingredient, substantially insoluble in nitroglycerin.

14. A modified blasting gelatin comprising at least 88% of nitroglycerin, nitrocellulose and from 3 to 6% of a fibrous, carbonaceous material.

15. A modified blasting gelatin comprising at least 88% of nitroglycerin, nitrocellulose an from 3 to 6% of wood pulp.

CLIF'FURD A. WOODBURY.