US2129367A - Gelatinous or semigelatinous blasting explosives - Google Patents

Description

Ratented Sept. 6, 1938 PATENT OFFICE GELATINOUS R BLASTING SEMIGELATINOUS ExrLosIvEs Vernon Harcourt Williams, Ardrossan,

Ayrshire,

Scotland, and-Bernard William Foster, Blackheath, London,

Great Britain No Drawing. No. 90,002.

8 Claims.

This invention relates to gelatinous or semi-,

gelatinous blasting explosives containing a quantity of nitroglycerine or other liquid nitric ester gelatinized with a proportion of nitrocellulose. In such explosive -.compositions oxidizing salts,

carbonaceous materials, nitro-compounds, explosive or power-producing salts and cooling salts are often included for the purpose of modifying the properties of the compositions.

The invention relates particularly but not exclusively to gelatinous or semi-gelatinous blasting explosives in which a proportion of cooling salts or the like has been included for the purpose of rendering the said explosives suitable for use in i5 fiery or dusty mines. Such explosives will be referred to hereinafter as safety explosives.

The gelatinous or semi-gelatinous character of an explosive composition is determined in part-by the proportion of liquid nitric ester and any other :0 liquid ingredients, and in part by the proportion and absorbency of any may be included in the composition. Common absorbents so included are carbonaceous materials, e. g. woodmeal, and these are'usually 5 characterized by a high absorbency. In gelatinous explosives the structure of the gelatinized nitric ester is retained to such an extent that the mix constitutes a coherent jelly. Such explosives are normally cartridged by an extrusion 0 process. In semi-gelatinized explosives, however, the structure is more or less discontinuous; and the liquid ingredients are only partly absorbed by the absorbent materials present and are distributed between the absorbents and the nitrocellulose. 5 Such explosives are normally too still in texture to be extruded. like fully gelatinized explosives. The ease with which an explosive composition can be cartridged, particularly by an extrusion process, is dependent upon its plasticity; and I this term is used hereinafter to indicate those properties of the composition by virtue of which it, can be worked under. pressure so that it assumes a coherent and compact form which, after deformation under pressure, does not regain its original shape when the pressure is released.

In both fully gelatinous and semi-gelatinous explosives it is advantageous to increase the plasticity of a given composition, due regard being paid to other requirements. Thus, for example, in gelatinous or semi-gelatinous explosive compositions it is known that the plasticity is largely accounted for by the proportion of nitro compound or nitric ester present, but, although there must be present a certain minimum proportion of the said materials in order to aflord the necessary England, Chemical Industries Limited Application In Great Britain July 26, 1935 absorbent materials that assignors to Imperial a corporation of July 10, 1936, Serial sensitivity, too great a proportion is undesirable on the grounds of economy, risk of exudation, and reduced safety. Moreover, a proportion of the nitric ester added may be absorbed by any unsaturated absorbent carbonaceous materials 5 present, and difiiculty has been experienced hitherto, particularly when the explosive compositions contain such materials, in obtaining a suitable increase of plasticity without unduly increasing the proportion of nitric-ester present.

The plasticity can also be increased by adding to the composition a proportion of a carbonaceous ingredient of low absorbency, such as starch, but such an addition causes a decrease in the oxygen value of the composition. Dufliculty. has also been experienced hitherto in producing safety explosives having bothsatisfactory plasticity and satisfactory oxygen balance. As a large proportion of cooling salts must be included in these explosives and as the total proportion of salts is limited, it is not practicable to include more than a limited quantity of oxidizing salts, which may be insuflicient to balance the negative oxygen value of 'the carbonaceous absorbents associated with the liquid nitric ester.

We have found that both the plasticity and safety of gelatinous or semi-gelatinous blasting explosives of the kind described may be improved by including in the composition a proportion of a clay or other clq-like inorganic material as hereinafter describe either in addition to the other ingredients of the composition, or wholly or in part in substitution for the carbonaceous absorbents which may be included normally.

It will be understood that, whereas the increase in plasticity afforded by the present invention is of practical value throughout the entire range of gelatinous and semi-gelatinous explosives, the improvement in safety is of practical value only when the compositions already 40 contain suflicient cooling salts, or have been otherwise modiiied, to bring them within the recognized class of safety explosives.

Throughout the present specification and claims attached thereto, the term plastic explosive shall be understood to refer to blasting explosives of the gelatinous and semi-gelatinous types.

' The terms clay" or plastic clay as employed in the present application shall be understood to refer to a member of the class of plastic aluminum silicates, that is, those aluminum silicates which normally exihibit plastic properties when in a finely divided state (whether or'not containing other metals as well as aluminium or' other acid groups as well as silicate as minor constituents 2 in their compositions). The clays employed are preferably those having an absorbency for nitroglycerine of the same order as that of starch. Amongst the clays that included, for instance, china clay, pipeclay, or bentonite. The clays are used in the finely divided state in which they normally exhibit their plastic properties, and those of them that have a high afiinity for water, for example bentonite, may, if desired, be employed in association with a small proportion of water but in the absence of free water. The presence of water in such manner is often of particular advantage, since it improves the plasticizing properties of the clay, and since it is fixed by the clay there is no risk of the loss of sensitiveness which might otherwise occur if free water were present in the mixture.

In putting the invention into effect, the quantity of the clay which we may employ may depend on circumstances, but useful efiects are ordinarily obtained with quite small quantities of the order of 2%-6%. In certain circumstances itmay be possible toincorporate larger quantities.

In general, the addition of a clay to a gelatinous or semi-gelatinous explosive in accordance with the present invention increases the plasticity, and reduces the magnitude of the oxygen value,

(whether positive or negative) in proportion to the amount of clay employed. It will be understood, however, that advantages of the invention may also he realized in practice in that simultaneous modifications in the nature and proportions of the other ingredients of the compositions for particular purposes may be made.

Thus, for example, in compositions containing a proportion of highly absorbent carbonaceous material a part or even the whole of such carbonaceous material may be replaced by the clay, and the resulting increase in plasticity may be suflicient to convert the semi-gelatine into a fully gelatinous .explosive. If, on the other hand,'it is desired primarily to reduce the proportion of liquid nitric ester, simultaneous replacement of part of the carbonaceous ingredient by clay will enable that to be effected without detriment to the plasticity, and with less risk of exudation. In both cases the final explosive will have an increased oxygen value in comparison with the original composition. i

In the particular case of safety explosives, the increase in safety specifically attributable to the use of clay or clay-like material in the preferred proportions is also of practical importance. The power of the explosive is, of course, reduced ac cording to the diluent effect of the clay, but the increase in safety more than compensates for this power reduction. If, however, the clay is substituted for an equivalent proportion of cooling salts, the power and oxygen value of the explosive are unaltered, and the safety increased.

The inventionis further illustrated by the following examples, in which the parts are "parts by weight.

Example 1 v Parts Nitroglycerine nitroglycol mixture- Nitrocotton 1.3 Dinitrotoluene f 3 Ammonium nitrate 45.! Sodium nitrate 10 Bentoni 5 Maize starch. 5

These ingredients were'incorporated in the normal manner, the clay and the maize starch being may be employed are added together. The plasticity of this explosive was about the same as an explosive made with 10 parts of 'maize starch instead of the 5 parts of clay and the 5 parts of starch, but the oxygen value per gm. of the unwrapped explosive was +5.1 as against -0.5. When wrapped the corresponding values were '0.9 and 6.5. This example illustrates the improvement of oxygen value at constant plasticity.

Example 2 Parts Nitroglycerine nitroglycol mixture 30 Nitrocotton 1.3 Dinitrotoluene 3 Ammonium nitrate 55.7 Bentonite 5 Water, absorbed in the bentonite 2 Maize starch 3 The oxygen value of this explosive unwrapped was +5.0, and its explosive .listic mortar, was 80% power, tested by the bal- (blasting gelatine=100 Example 3 Parts Nitroglycerine nitroglycol mixture 25 Nitrocotton"- 0. 7 Dinitrotoluene 3.0 Ammonium-nitrate 54.3 Sodium nitrate 7.0 Bentonite r 5.0 Maize star h 5.0

The oxygen value of the unwrapped explosive was +5.5, the power 76% of blasting gelatine, and the plasticity about the same as in Examples 1 and 2.

I Example 4 Parts Nitroglycerine nitroglycol mixture 25 Nitrocotto 0.8 Dinitrotoluene 3.0 Ammonium nitrate 46.2 Sodium chlor 18.0 Wheat flour- 2.0 China clay- 5.0

The ingredients were mixed together as in the previous examples, and the explosive was com pared with a s 'lar composition including the same proportions of ingredients except that china clay was omitted and the salt increased by a correspondingmmoun of the power of blasting gelatine, and an oxygen balance of +4.7. The composition containing china clay, however, was the more plastic, and its safe charge limit in gas was 10 oz. as compared with 8 oz. for the explosive without china clay. This example shows the increase in safety of a safety explosive obtained by the present invention.

We claim:

1. A plastic explosive composition comprising a liquid explosive nitric ester, a gelatinizing agent for said nitric ester, and a plastic clay. r

2. A plastic explosive composition comprising a liquid explosive nitric ester, a gelatinizing agent for said nitric ester, and from 2 to 6% of a plastic clay.

3. A plastic explosive composition comprising a liquid nitric ester of an aliphatic alcohol con'-. taining at least two hydroxyl groups, a gelatinizing agent for said liquid nitric ester, and a plastic clay.

4. The explosive composition of claim 3, in which the liquid nitric ester comprises nitroglycerin.

5. The explosive composition of claim 3, in which the gelatinizing agent ester comprises nitrocotton.

Each composition had 58% for the liquid nitric 1 6. A plastic explosive composition comprising nitroglycerin gelatinized by means of nitrocotton,

and a plastic clay in an amount suflicient to impart improved plasticity and safety in the presence of inflammable gases.

7. A plastic safety explosive composition comprising nitroglycerin, nitrocotton, a cooling salt, and a plastic clay.

8. A plastic explosive composition comprising a liquid explosive nitric ester, a gelatinizing agent for said nitric ester, and a plastic clay, said clay being associated with a small proportion of water,

free water being absent from said explosive com- 5 position.

.VERNON HARCOURT WILLIAMS. BERNARD WILLiAM FOSTER.