US3197511A - Nitropolystyrene - Google Patents

Description

United States Patent No Drawing. Filed May 7, 1964, Ser. No. 365,794 4 Claims. (Cl. 260-644) This application is a continuation-in-part of application Serial No. 155,498 filed by us on November 28, 1961, for Nitropolystyrene, now US. Patent No. 3,154,448.

The invention relates to nitropolystyrene.

The invention comprises, more particularly, nitrated atactic polystyrene of relatively low molecular weight or nitrated isotactic polystyrenes.

These compounds are useful as explosives of velocity of detonation that lies in a range hereto not supplied, e.g., about 1,0002,000 m./sec. for the dinitro compounds. This is far above that of standard explosive mixtures of combustible and oxidizing components such as black powder (about 400 m.) but far below the velocity of TNT and like nitroexplosives (4,0008,000 m.). For a given degree of nitration, on the other hand, the explosive force of nitropolystyrene is strong as compared, for instance, with nitrated toluene. Thus our dinitropolystyrene in the metal plate test for brisance gives, per unit of weight, a penetration equal to or in excess of that given by trinitrotoluene.

Our dinitropolystyrene melts above about 260 C., if at all, as compared with melting temperatures within the range about 52-70 C. for the dinitrotoluenes and 80-l12 C. for the various isomeric trinitrotoluenes.

The nitrated polystyrene, either alone or compounded, may be formed into blocks, i.e., shape retaining plasticbonded explosives that can be molded into variously formed masses to fit spaces in which the explosive is to be set and then fired. Such are the recesses in rivets that are to be expanded by firing explosive in the said recesses.

As to materials, we obtain particularly satisfactory results including high density, causing more of the explosive to be insertable into a given drill hole or other space, when we use isotactic polystyrene as the material to be nitrated. We may use also for most purposes, the product of nitration of atactic polystyrene of such relatively low molecular weight that the product, after the nitration will be below about 50,000. The polystyrene recommended for making such product is of molecular weight not substantially above about 80,000 before the nitration. Either of the polystyrenes after nitration and purification by washing may be blended with a nitrated C -C polyol plasticizer as, for example, nitroglycerine of dynamite grade, monoor dinitroglycol, or dinitropentaerythritol in the proportion of -50 parts for 100 of the nitrated polystyrene.

A convenient acid for nitrating the polystyrene is mixed nitric and sulfuric acids with substantial sulfur triox de content. Such mixed acid is obviously anhydrous. We nitrate to an average nitrogen content corresponding approximately to monoor dinitropolystyrene, the latter having two N0 groups for each monomeric styrene unit (wt. 104) represented in the polymer.

As the stabilizer to decrease the autocatalytic decomposition of the nitropolystyrene, if desired, we use one of the organic acceptors of acid so as to reduce the pH that otherwise would result as acid is liberated by slow de composition. Examples of such acceptors to be used are nitrogen bases, that is, salt formers with acids such as diphenylamine, tetramethylaniline, and urea. The stabilizer is used to advantage in the amount of about 0.1-2 parts for 100 parts of the nitropolystyrene.

As a component, it any, to modify the explosive properties of the nitropolystyrene, we may use the ammonium nitrate, sodium or potassium nitrate, trinitrotoluene or the like within the range 50500 parts for 100 parts of the nitropolystyrene.

The components may be simply admixed but for many purposes, such as explosive blocks, should be bonded by the thermoplastic nitropolystyrene'iinto a firm, shape retaining mass.

The invention will be further illustrated by description in connection with the following specific examples of the practice of it. In these examples and elsewhere herein proportions are expressed as parts by weight.

Example 1 Dinitro-isotactic-polystyrene is made as follows:

Fifty parts of isotactic polystyrene, made as described by Natta in Die Makromalekulare Chemie, vol. 16, pp. 213-237 (1955), and elsewhere, is gradually added with stirring to an anhydrous mixture of 450 parts of nitric acid of specific gravity 1.50, 200 parts of sulfuric acid of sp. gr. 1.84 and 100 parts of sulfur trioxide, the latter being dissolved in advance in the sulfuric acid. The temperature of the mixing during the introduction and solution of the polystyrene is maintained at 15 -20 C. by external cooling. After all of the polystyrene has been introduced and dissolved, the temperature is raised to 5055 C. and kept within that range for 2 hours, i.e., until the reaction that has followed the mixing is substantially completed.

The resulting mixture of nitro-isotactic-polystyrene and spent acids is cooled to 25 C. and poured into approximately 5,000 parts of cold Water. This precipitate, the nitropolystyrene, is separated from the aqueous phase by decantation, washed with cold water to remove acid. and finally with a dilute solution of sodium carbonate and ammonium hydroxide until the washings are not acidic to Congo red.

The product is dried at C., to a firm hard relatively dense solid. Stabilizers are not necessary for the nitrated isotactic product. The stabilizers and/or other compounding ingredients shown herein may be admixed, however, as in the proportion of 0.5 part of the stabilizer and 200 parts of ammonium nitrate or TNT component for parts of the nitropolystyrene.

Example 2 The procedure and compositions of Example 1 are used except that the polystyrene used for the nitration is the commercial atactic polystyrene of molecular weight about 80,000. The yield of the washed and dried product is 70 parts or 99.5% of theory on the basis of the polystyrene used.

The product starts to decompose on heating gradually at 260 C. and is not fully melted at temperatures as high as 300 C. The nitrogen content is 14.2%. The theory is 14.3% for dinitropolystyrene having 2 N0 groups for each monomeric styrene unit.

. Overall Depth of Explosive Density of Penetration,

Explosive, g. inch per ml.

Dinitropolystyrene 0. 65 0. 145 Do 0. 67 0. 153 Trinitrotoluenm- 0.95 0. 194

Corrected for its lower density, the dinitropolystyrene explosive on an equal weight basis shows a calculated brisance, as indicated by the depth of penetration, at least approximately equal to that of the more highly nitrated trinitrotoluene. I

In spite of the high brisance, the dinitropolystyrene has a relatively low velocity of detonation, about 1,000-2000 meters per second, as compared to about 4,700 for TNT at a density of 0.95 g./ml. This rate for our product adapts it especially for dispersing, to the right degree, materials mixed therewith that are to be disseminated into air.

Example 3 The procedure and composition of Example 2 are used except that the washed and dried dinitropolystyrene is mixed with 0.5 %1% of its Weight of each of the following stabilizers used separately and in turn: diphenylamine, tetramethylaniline and urea, to retard development of instability on storage.

Example 4 The procedure and composition of Example 2 are used except that the washed and dried nitropolystyrene is parts of sodium nitrate and potassium nitrate used separately and in turn. The nitrate used supplies available oxygen during the explosion of the composition and thus promotes combustion to the stage of increased energy release and less smoking.

Example 5 The procedure and composition of Example 3 are used except that the washed and dried dinitropolystyrene is mixed thoroughly and in the amount of 100 parts with 500 parts of ammonium nitrate. The ammonium nitrate provides oxygen for the more nearly complete combustion of the dinitropolystyrene and also its own powerful explosive force.

It will be understood that it is intended to cover all changes and modifications of the examples of the invention herein chosen for the purpose of illustration which do not constitute departures from the spirit and scope of the invention.

We claim:

1. A compound selected from the group consisting of nitrated atactic polystyrene of average molecular weight below about 50,000 after nitration and nitrated isotactic polystyrene, the compound being an explosive of brisance on detonation approximately equal at least to that of TNT and of velocity of detonation not above about half that of TNT.

2. As an explosive, dinitro-isotactic-polystyrene.

3. As an explosive, dinitro-atactic-polystyrene of average molecular weight below about 50,000.

4. The process of nitrating polystyrene which includes maintaining the polystyrene in contact with an anhydrous solution of nitric acid, sulfuric acid and sulfur trioxide until the reaction that ensues is completed, then adding water to precipitate the resulting nitropolystyrene and washing the precipitated product to remove acid ther from.

References Cited by the Examiner UNITED STATES PATENTS 2,572,420 10/51 Zenftman et al. 149-105 X CARL D. QUARFORTH, Primary Examiner.

Claims (1)

1. A COMOUND SELECTED FROM THE GROUP CONSISTING OF NITRATED ATACTIC POLYSTYRENE OF AVERAGE MOLECULAR WEIGHT BELOW ABOUT 50,000 AFTER NITRATIONAND NITRATED ISOTACTIC POLYSTYRENE, THE COMPOUND BEING AN EXPLOSIVE OF BRISANCE ON DETONATION APPOXIMATELY EQUAL AT LEEAST TO THAT OF TNT AND OF VELOCITY OF DETONATION NOT ABOVE ABOUT HALF THAT OF TNT.