US3344005A - Pentaerythritol tetranitrate-trimethylolethane trinitrate explosives - Google Patents

Description

United States Patent 3,344,005 PENTAERYT 5": TQL TETRANITRATE-TRIMETH- YLOLETHANE TRINITRATE EXPLOSIVES Jesse B. Bronstein, Allentown, and George L. Grifiith,

Coopershurg, Pa., assignors to Trojan Powder Company, Allentown, Pa., a corporation of New York No Drawing. Filed Feb. 23, 1966, Ser. No. 529,212 8 Claims. (Cl. 14938) ABSTRACT OF THE DISCLOSURE This invention relates to explosive compositions based on a combination of pentaerythritol tetranitrate and tri methylolethane trinitrate as explosive sensitizers, and more particularly, to explosive compositions comprising pentaerythritol tetranitrate, trimethylolethane trinitrate, and an inorganic oxidizer, such as an inorganic nitrate, and to a process for forming the same.

Pentaerythritol tetranitrate is a high explosive that is in wide use today. Physically, it is a crystalline solid of high melting point, crystallizing from water in white tetragonal crystals having a melting point of 253 C. These physical properties distinguish it from the liquid nitric acid esters, such as propylene glycol dinitrate, nitroglycerine, and butylene glycol dinitrate. The liquid esters are more difficult to use than the solid pentaerythritol tetranitrate, and usually are employed adsorbed on a solid material or formulated as a gel. Even the low melting solids, such as erythritol tetranitrate, are not as advantageously used in powdered explosive formulations as pentaerythritol tetranitrate.

The problem with the use of pentaerythritol tetranitrate is its high sensitivity to initiation upon shock impact. It is in fact extraordinarily sensitive to initiation, and is detonated by 0.01 gram of lead azide, whereas tetryl requires 0.025 gram of lead azide for certain detonation. This sensitivity and its great brisance combine to make pentaerythritol tetranitrate exceptionally serviceable in compound detonators, but the fact that it is so sensitive makes it rather dangerous to handle, and thus its use presents somewhat of a problem.

In order to reduce sensitivity, pentaerythritol tetranitrate has been combined with other materials. The difiiculty with such combinations, however, is that the resulting mixture is usually much less sensitive to initiation than pentaerythritol tetranitrate, and it has not been possible to formulate a mixture which is less sensitive to impact but not appreciably less sensitive to initiation by a detonator.

Stettbacher, Z. ges. Schiessu. Sprengstoffw, 26, 8, 39, suggested several dynamite-like explosives, containing both pentaerythritol tetranitrate and nitroglycerine, which he called Penthrinit. Naol'lm, Z. ges. Schiessu. Sprengstolfw 26, 8, 42, reported tests of such compositions 'ice based on ammonium nitrate with and without pentaerythritol tetranitrate. Stettbacher, Swiss Patent No. 137,476, described the formulation of gelatinized plastic explosive compositions based on pentaerythritol tetranitrate combined with some 10 to 30% of a fluid nitric ester, such as nitroglycerine or nitroglycol, which he considered suitable for loading shells and detonators. All of these formulations, however, have the defect that the resulting pentaerythritol tetranitrate combinations have a considerably lesser detonator sensitivity. Whereas pentaerythritol tetranitrate can be detonated by 0.01 gram of lead azide, for example, Stettbachers composition of Swiss Patent No. 137,476 is said to be initiated with 0.04 gram of lead azide, a sensitivity one-fourth as great as that of the pentaerythritol tetranitrate, and in fact less sensitive even than tetryl, which requires 0.025 gram of lead azide.

In accordance with the invention, explosive compositions of high detonator sensitivity, approximating that of pentaerythritol tetranitrate itself, but of considerably less sensitivity to impact, are prepared by combining pentaerythritol tetranitrate with trimethylolethane trinitrate. The explosive compositions in accordance with the invention are based on a combination of pentaerythritol tetranitrate and trimethylolethane trinitrate as explosive sensitizers. Such compositions can be formulated with additional ingredients, including inorganic oxidizers, such as an inorganic nitrate, fuels, gelatinizing agents and the like, the conventional ingredients used in explosive formulations of the type desired.

Trimethylolethane trinitrate is a liquid, and consequently, in combinations with granular pentaerythritol tetranitrate, explosive formulations of very desirable physical properties can be prepared, having a consistency ranging from a soft extrudable consistency to a solid, hard-packing granular material.

Inasmuch as the pentaerythritol tetranitrate is solid, and the trimethylolethane trinitrate is a liquid, it is thought that the difierence in sensitivity to shock of the explosive compositions of the invention is due to the trimethylolethane trinitrates wetting the pentaerythritol tetranitrate, reducing its sensitivity to shock, while not affecting its sensitivity to initiation by a detonator.

The relative proportion of trimethylolethane trinitrate is determined by the amount required to reduce sensitivity to shock, while not significantly reducing detonator sensitivity. The maximum amount is established as that .which can be retained homogeneously in the composition. In general, the amount of trimethylolethane trinitrate lies within the range from about 5 to about 55%, and the proportion of pentaerythritol tetranitrate is within the range from about to about 45%, based on the total explosive sensitizer of the composition. A composition containing upwards of 30% trimethylolethane trinitrate will be of a soft consistency, which is extrudable using a screw-type or cylinder-type extruder. Compositions in which the proportion of trimethylolethane trinitrate is less than 30% are granular solids. If the composition contains solid ingredients in addition to the pentaerythritol tetranitrate, such as an inorganic oxidizer and a solid fuel, then the proportion of the trimethylolethane trinitrate to give a soft consistency is based on the total weight of solids in the composition.

The trimethylolethane trinitrate imparts a cohesiveness to the explosive mixtures of the invention, which reduces dusting, and increases safety. The compositions are best formulated as granules which will retain their shape, and are essentially nonfriable.

The principal explosive sensitizers employed are pentaerythritol tetranitrate and trimethylolethane trinitrate. Additional sensitizers can be used in substitution for a proportion of the pentaerythritol tetranitrate and/ or trimethylolethane trinitrate, in an amount up to approximately 50% of the total explosive sensitizer. These include trinitrotoluene, dipentaerythritol hexanitrate, mannitol hexanitrate, sorbitol hex-anitrate, sucrose octanitra-te, ethylene glycol dinitrate, diethylene glycol dinitrate, Pentolite (an equal parts by weight mixture of pentaerythritol tetranitrate and trinitrotoluene), nitrostarch, Cyclonite (RDX, cyclotrimethylene trinitramine), Composition B (a mixture of up to 60% RDX, up to 40% TNT and 1 to 4% wax), Cyclotol (Composition B without the wax), dinitrotoluene, and tetryl. A composition composed solely of pentaerylthritol tetranitrate and trimethylolethane trinitrate as the only explosive sensitizers is preferred, because it gives the greatest explosive effect.

In formulating explosive compositions, these explosive sensitizers are preferably used with an inorganic oxidizer salt to compensate for the oxygen deficiency of the pentaerythritol tetranitrate and the trimethylolethane trinitrate. Preferably, the oxidizer employed is an inorganic nitrate.

Ammonium nitrate and nitrates of the alkali and alkaline earth metals, such as sodium nitrate, potassium nitrate, calcium nitrate, magnesium nitrate, strontium nitrate, and barium nitrate are exemplary inorganic nitrates. Ammonium nitrate and mixtures of ammonium nitrate and another nitrate in minor proportion are preferred. Excellent results are obtained with mixtures of ammonium nitrate and sodium nitrate, and such mixtures are frequently preferred over ammonium nitrate alone.

As the inorganic oxidizer, there can also be used a chlorate or a perchlorate of an alkali or alkaline earth metal, such as sodium chlorate, potassium chlorate, barium chlorate, sodium perchlorate, potassium perchlorate, barium perchlorate and calcium perchlorate. Mixtures of nitrates, chlorates, and perchlorates; of nitrates and chlorates; of nitrates and perchlorates; and of chlorates and perchlorates, can be used.

When mixtures of ammonium oxidizer and the other oxidizer are used, the relative proportion of ammonium oxidizer is important for good explosive shock and power. The ammonium oxidizer is employed in a proportion Within the range from about 50 to 95% by weight of the total oxidizer, and the other oxidizer or oxidizers in the proportion of from about 5 to about 50% of the total oxidizer. For optimum power, the proportions are from 80 to 90% ammonium oxidizer, and from to other oxidizer or oxidizers. The proportions of oxidizers selected within these ranges will depend upon the sensitivity and explosive effect desired, and these, in turn, are dependent upon the particular oxidizer used.

The inorganic oxidizer can be fine, coarse, or a blend of fine and coarse materials. Mill and prill inorganic oxidizers are quite satisfactory. For best results, the inorganic oxidizers should be fine-grained.

The relative proportions of oxidizer and explosive sensitizers will depend upon the sensitivity and explosive power desired, and these, in turn, are dependent upon the particular oxidizer and explosive sensitizers. For optimum effect, the oxidizer is used in an amount within the range from about 10 to about 75%, and the explosive sensitizer in an amount within the range from about 5 to about 40% by weight of the explosive composition. From about to about explosive sensitizer, and from about 50 to about 70% inorganic oxidizer give the best results. The proportions of oxidizers selected within these ranges will depend upon the sensitivity and explosive effect desired, and these in turn are dependent upon the particular oxidizer used.

In addition to these materials, the explosive compositions of the invention can include a fuel, which can be either a metal fuel or a carbonaceous fuel, in an amount of from about 0.5 to about 30%.

Satisfactory metal fuels include aluminum, which can be in the form of powder or flake, or in a very finely-divided form known as atomized aluminum; ferrosilicon and ferrophosphorus. The metal fuel will usually comprise from about 0.5 to about 25% of the composition.

A carbonaceous fuel can also be included, either as the only fuel or in combination with a metal fuel. Satisfactory carbonaceous fuels include powdered coal, petroleum oil, coke dust, charcoal, bagasse, dextrine, starch, wood meal, wheat flour, bran, pecan meal, and similar nut shell meals. The carbonaceous fuel will usually be used in an amount within the range from 0.5 to about 30%.

Mixtures of metal and carbonaceous fuels can also be used, if desired.

Stabilizers can be included in an amount within the range from about 0.3 to about 2% of the composition. Zinc oxide, ethyl centralite, diphenylamine, carbazole, calcium carbonate, aluminum oxide and sodium carbonate are useful stabilizers.

For some purposes, the compositions of the invention can be formulated as slurries, using an inert liquid such as water or petroleum oil as the suspending liquid. The amount of liquid that is used is more than would be absorbed by the solid ingredients, and suificient to produce a slurry. The slurry can have any desired consistency, from a thin, readily flowable material, to a viscous material of a semi-solid consistency. As little as 0.5% liquid may suffice. Usually, not more than 30% liquid need be used.

In order to prevent large amounts of unabsorbed liquid from decreasing the consistency unduly, a liquid-soluble or liquid-dispersible thickener can be added to take up the liquid. The particular material employed will depend upon the liquid that is used, Water-soluble or water-dispersible thickeners being used when water is the liquid, and oil-soluble or oil-dispersible thickeners being used when the oil is the liquid. Various gums, such as guar gum and cross-linked guar gum, can be used, as well as carboxymethylcellulose, methyl cellulose psyllium seed mucilage, and pregelatinized starches, such as Hydroseal 3B, as well as silica aerogels, finely-divided silicas, inorganic gelling agents such as alumina, attapulgite, bentonite, and like materials.

The explosive composition is readily prepared by simple mixing of the ingredients. The trimethylolethane trinitrate, since it is a liquid, is usually absorbed by or adsorbed on the solid ingredients. In many cases, it may be preferable to mix the trimethylolethane trinitrate and pentaerythritol tetranitrate separately, so that the trimethylolethane trinitrate is incorporated with the ,pentaerythritol tetranitrate particles, and then add the remaining materials. In most cases, the solid materials, including the inorganic oxidizer and explosive sensitizers, fuels, and antacid, if any, would be mixed first to form a homogeneous blend, and the trimethylolethane trinitrate and any other liquid ingredients, such as oil and water, would then be added, with stirring until a homogeneous mixture is formed.

The pentaerythritol tetranitrate, trimethylolethane trinitrate, and ohter explosive ingredients that are heatsoftenable or liquefiable also can be combined by mixing the liquid trimethylolethane trinitrate, the softened or liquid additional ingredients and slurry of pentaerythritol tetranitrate in a liquid dispersant which is inert to both at a temperature below the denotation temperature of both. In this process, the resulting combined particles can be brought to the surface of the liquid dispersant, and skimmed off. The resulting mixture can be used as such, or screened and pelleted, or rolled into a sheet. Additional explosive components, such as the inorganic oxidizer, a fuel and antacid, can be incorporated with the particles at this stage, or can be incorporated with the aqueous slurry of pentaerythritol tetranitrate prior to combination with the trimethylolethane trinitrate, and other explosive ingredients. For example, if the liquid dispersant is an aqueous solution saturated with respect to ammonium nitrate, the particles that are obtained as a result are composed of a mass of pentaerythritol tetranitrate and other explosive ingredients containing the trimethylolethane trinitrate, and containing the ammoniurn nitrate in its pores and on its surface in the form of crystals.

In order to form the mixture of pentaerythritol tetranitrate, trimethylolethane trinitrate and other ingredients quickly and efliciently, the mixing should be carried out at a high speed. Either rotary mixing or reciprocating mixing can be employed, the former being preferred.

The actual speed of mixing depends on the type of mixing used, the quantities and flow rates of the explosive ingredients, the type of dispersant, the mixing temperature, and the form of product desired. High mixing temperatures can be used without danger of detonation, because the mixing is conducted in the liquid dispersant.

Any liquid which is liquid at the mixing temperature, and unreactive with and not imparting deleterious effects to the explosive components or other ingredients employed can be used in this process. Water is an excellent dispersant.

This process can be carried out as a batch procedure or as a continuous process. In the continuous process, the trimethylolethane trinitrate and the slurried pentaerythritol tetranitrate are fed to the mixer at the same rate as the mixed product is drawn oil from the surface of the liquid dispersant.

These explosive compositions can be filled into explosive containers of any type, using conventional filling equipment suited to the particular consistency of the composition. A plastic composition is readily extruded into the container. A powdered, granulated, or pelleted formulation is conveniently filled by conventional screw fillers.

The following examples, in the opinion of the inventors, represent the best embodiments of their invention.

Examples 1 and 2 A series of explosive mixtures was prepared from pentaerythritol tetranitrate, class 3, dry, and trimethylolethane trinitrate. The pentaerythritol tetranitrate was thoroughly mixed with the liquid trimethylolethane trinitrate in the proportions shown in Table I which follows. Impact sensitivity and detonator sensitivity were then determined.

Impact sensitivity was evaluated using the following test procedure, First, a 2 kg. Weight was dropped on 0.1 g. samples of the mixture, starting at a height of 100 cm., decreasing the height in 5 cm. increments until no detonation occurred. This procedure was then repeated using a kg. weight. The minimum height at which detonation occurred was then noted in the table.

Detonator sensitivity was determined by filling the composition into a cartridge 1 inch in diameter and 4 inches long. Detonator sensitivity was determined using the standard cap series.

The following results were obtained:

Control A shows that the pentaerythritol tetranitrate used had a detonator sensitivity of a No. 1 cap, and a high impact sensitivity. The mixture of Examples 1 and 2 also had a No. 1 cap, detonator sensitivity, but the impact sensitivity was very greatly reduced. Example No. 1 was approximately 50% less sensitive than Control A, and Example 2 was approximately one-third as sensitive as Control A.

Example 3 Dry stick powders were prepared, using the 70:30 mixture of Example 2 and pentaerythritol tetranitrate mixed with the other ingredients shown in the Table below.

Cartridges 1 inch in diameter by 4 inches long were filled using the above compositions. These cartridges were tested for impact sensitivity to a 10 kg. and to a 2 kg. weight, and detonator sensitivity. The results are given in Table II.

TABLE 11 Impact Sensitivity Detonator Example Explosive Sensitivity N 0. Composition 1" x 4" 10 kg. wt. 2 kg. wt. cartridge Control PETN 5 25 N0. 1. 4 70:30 mixture 5 40 No. 1.

These results confirm the lower impact sensitivity and equivalent detonator sensitivity of the mixture over pentaerythritol tetranitrate, when used inan explosive composition.

The percentages of the components of the compositions in the specification and claims are all given by weight, and are by weight of the entire composition unless otherwise indicated.

Having regard to the foregoing disclosure, the following is claimed as the inventive and patentable embodiments thereof:

1. An explosive sensitizer composition consisting essentially of an amount within the range from about to about 45% of pentaerythritol tetranitrate, and an amount within the range from about 5% to about 55% of trimethylolethane trinitrate, sufiicient to lessen the impact sensitivity of the pentaerythritol tetranitrate without significantly reducing the detonator sensitivity.

2. An explosive sensitizer composition in accordance with claim 1, wherein the pentaerythritol tetranitrate and trimethylolethane trinitrate are in the form of paricles forming a homogeneous non-segregating mixture.

3. An explosive composition in accordance with claim 1, comprising in addition an inorganic oxidizer salt.

4. An explosive composition in accordance with claim 1, comprising in addition a fuel.

5. An explosive composition in accordance with claim 4, wherein the fuel is a carbonaceous fuel, in an amount within the range from about 0.5 to about 30%.

6. An explosive composition in accordance with claim 4, wherein the fuel is a metal fuel in the amount within the range from about 0.5 to about 25%.

7. An explosive composition comprising an explosive sensitizer consisting essentially of from about 95% to about 45% of pentaerythritol tetranitrate, and from about References Cited UNITED STATES PATENTS Parodi-Delfino 14993 X Russell 14962 X Williams et a1. 14938 X Matuszko et a1. 149-38 Grifiith et a1. 149-38 BENJAMIN R. PADGETT, Primary Examiner. s. I. LECHERT, JR., Assistant Examiner.

Claims (4)

1. AN EXPLOSIVE SENSITIZER COMPOSITION CONSISTING ESSENTIALLY OF AN AMOUNT WITHIN THE RANGE FROM ABOUT 95% TO ABOUT 45% OF PENTAERYTHRITOL TETRANITRATE, AND AN AMOUNT WITHIN THE RANGE FROM ABOUT 5% TO ABOUT 55% OF TRIMETHYLOLETHANE TRINITRATE, SUFFICIENT TO LESSEN THE IMPACT SENSITIVITY OF THE PENTAERYTHRITOL TETRANITRATE WITHOUT SIGNIFICANTLY REDUCING THE DETONATOR SENSITIVITY.

3. AN EXPLOSIVE COMPOSITION IN ACCORDANCE WITH CLAIM 1, COMPRISING IN ADDITION AN INORGANIC OXIDIZER SALT.

4. AN EXPLOSIVE COMPOSITION IN ACCORDANCE WITH CLAIM 1, COMPRISING IN ADDITION A FUEL.

6. AN EXPLOSIVE COMPOSITION IN ACCORDANCE WITH CLAIM 4, WHEREIN THE FUEL IS A METAL FUEL IN THE AMOUNT WITHIN THE RANGE FROM ABOUT 0.5 TO ABOUT 25%.