US3018201A - Gelatinous explosive composition - Google Patents

Description

a t ali x-- 3,038,2di Patented Jan. 23, 1962 3,018,201 GELATHNOUS EXPLUSEVE CUMPOSETHGN Jack M. Downard, Fiorence, Ni, assignor to Hercules Powder Company, Wilmington, Del, a corporation or Delaware No Drawing. Filed Jan. 6, 1951, Ser. No. 204,815 9 Claims. (Cl. 1149-49) This invention relates to detonative explosives and more particularly to gelatinous detonative explosives and a method for their manufacture.

Gelatinous and semigelatinous dynamites have been made for years using a nitrocellulose-nitroglycerin gel. As early as 1878, A. Nobel developed a dynamite of this type. For many years the lowest strength of gelatin dynamite made was a forty percent straight gelatin dynamite containing 35% of nitroglycerin.

In the development of economical gelatin dynamites which still retained good water resistance, the nitroglycerin content was gradually reduced to 25%27%, While incorporating large percentages of ammonium nitrate to maintain a high strength. This was about the minimum nitroglycerin content that could be achieved while maintaining a really plastic gelatinous consistency adapted to packing on the gelatin-type cartridging machine. Howei'er, subsequently, 'semiplastic explosives of high strength and good water resistance were obtained with as little as 20% of gelatinized liquid explosive. These are called semigelatin dynamites, and are generally packed on a Hall-type packing machine which is more economical than using the gelatin-type cartridging machine.

In copending application Serial No. 754,275, filed June 12, 1947, of which the present application is a continuation-impart, there are disclosed high strength gelatinous explosives which have a greatly reduced nitroglycen'n content or else contain no liquid explosive nitric ester at all. These explosive compositions are formed from high explosive material of the group consisting of liquid explosive nitric esters, nitrocellulose, nitrostarch and crystalline high explosives, and from about 1% to about 10% of a nonexplosive gel. The nonexplosive gels are prepared by gelling a nonvolatile, Water-insoluble petro leum hydrocarbon from the group consisting of petrolatum, parafiin base oils, naphthene base oils, intermediate base oils, cylinder oil, and bright stock with a petroleum-soluble elastomeric gelling agent of the group consisting of natural rubber, synthetic rubber and polyisobutylene. uch explosive compositions are preferably prepared by combining the hydrocarbon and gelling agent to initially form the nonexplosive gel. If carbonaceous ingredients are employed, they are preferably initially admixed with the nonexplosive gel. This gel mixture is then reduced to individual units and mixed with the explosive components of the composition.

Of the synthetic elastomeric gelling agents disclosed and claimed in the copending application Serial No. 754,275, now Patent No. 2,537,039, issued January 9, 1957, polyisobutylene and Buna S (copolymer of butadiene-styrene) have been found to give optimum results. The relatively less expensive butyl rubbers (copolymers of isoprene-isobutylene) are operable in the invention therein disclosed but are not preferred gelling agents because their use requires a substantially greater amount of gelling agent to obtain the desired physical characteristics in the final gelatinous composition. When enough butyl rubber is used to obtain these characteristics, the resulting explosive compositions are less sensitive to standard primers and slightly less powerful than similar compositions containing the preferred gelling agents.

Now in accordance with the present invention it has been discovered that excellent gelatinous explosives can be prepared by employing a nonexplosive gel containing a copolymer of isoprene and isobutylene which has been vulcanized by a suitable cross-linking or vulcanizing agent. Generally described, the present invention is a detonative, gelatinous explosive composition comprising high explosive material of the 'group consisting of liqud explosive nitric esters, nitrocellulose, nitrostarch and crystalline high explosives; and from about 1 to about 10% of a nonexplosive gel containing at least one substantially nonvolatile, Water-insoluble petroleum hydrocarbon of the group consisting of petrolatum, paraffin base oils, naphthene base oils, intermediate base oils, cylinder oil, and bright stock; and a vulcanized copolymer of isobutylene and isoprene. A further embodiment of the invention is a process for preparing high strength detonative gelatinous explosive compositions which comprises dissolving a copolymer of isobutylene and isoprene in a substantially nonvolatile, water-insoluble petroleum hydrocarbon of the group consisting of petrolatum, paraflin base oils, naphthene base oils, intermediate base oils,

cylinder oil and bright stock; dispersing a vulcanizing agent in the resulting solution, heating the solution at a vulcanizing temperature until thickening is obtained, cooling the resulting nonexplosive gel and admixing high explosive material with the gel to form a gelatinous explosive containing between 1 and 10% of the nonexplosive gel.

The copolymer of isoprene and isobutylene may have different molecular weights depending on the degree of polymerization. It will be understood, therefore, that in combination with a given petroleum hydrocarbon, varying amounts of the copolymer may be used depending on the desired consistency of the nonexplosive gel after vulcani- Zation of the copolymer. In general, it is preferred to employ the copolymer in an amount constituting from about 520% by weight of the nonexplosive gel. For optimum results it is further preferred that the unvuloanized copolymer have an ML viscosity at 212 F. at 8 minutes of over 40. The higher viscosities are preferred since it requires less of the higher molecular weight material to give gels of the desired consistency.

Having generally described the invention, the following examples are presented to illustrate specific embodiments thereof.

Example 1 GR-ll8 butyl rubber was cut into one-eighth inch squares and dissolved in ten times its weight of toluene with vigorous stirring at room temperature. Suflicient S.A.E. 10 lubricating oil (Esso) was then added to give a 15% solution of rubber in oil after the toluene was boiled oif by heating. When the solution was cooled to room temperature, 0.5% sulfur and 2.0% tetramethyl thiuram disulfide (Toads promoter) were added and thoroughly dispersed in the gel. The gel was then heated from room temperature to 170 C. with continuous stirring over a period of 45 minutes. The resulting wellconsolidated gel had a Brookfield viscosity at 40 C. of 1570 poises, While the unvulcanized gel had a Brookfield viscosity at 40 C. of only 470 poises.

Example 2 A uniform gelatinous explosive composition was prepared byhand kneading of cyclonite (cyclomethylenetrinitramine) into 5% by weight of the nonexplosive gel of Example 1. The cyclonite had the following screen analysis:

Percent On 80 mesh 20 On 100 mesh 8 On 140 mesh 29 On 200 mesh 16 Through 200 mesh 27 The resulting composition was packaged in 1% inch by 8 inch cartridges which had an average weight of 212 g. The cartridge count was 107. The composition had very good plasticity and its consistency was excellent, showing whiskers when pulled apart. In the conventional halvedcartridge gap sensitivity test the cartridges failed at 4 inches and shot at 3 inches. The detonation velocities were determined to be 7640 m./sec. and 7560 m./sec.,, respectively, for two cartridges tested.

Example 3 A gelatinous explosive composition was prepared which incorporated the gel of Example 1 and which had the following formula:

This composition was prepared as follows: The gel, wood pulp and corn starch were first uniformly admixed by kneading. The nitroglycolmitroglycerin solution was placed in a Shrader Bowl mixer and pregelled with the nitrocellulose. All the dope ingredients were then added and mixed. Then the non-explosive gelwood pulp-corn starch dough was added and the composition was mixed to uniformity. This composition exhibited very good plasticity and consistency. Eight by 1% inch cartridges of the composition weighed 198 g. and had a count of 115. In the gap sensitivity test, all cartridges shot at 4 inches. Two cartridges were tested for detonation velocities which were found to be 2940 and 2950 m./sec., respectively.

From the foregoing examples, it will be seen that by vulcanizing or cross-linking the butyl rubber employed in the nonexplosive gel, excellent results can be obtained. Consequently, the more readily available and more economical butyl rubbers may now be advantageously employed.

Although preferred it is not necessary to employ an intermediate solvent such as toluene in order to form the preliminary gel of the petroleum hydrocarbon and butyl rubber. Instead the butyl rubber may be dissolved in the petroleum hydrocarbon directly by use of suitable agitation and temperatures. Furthermore, the butyl rubber can be initially vulcanized and then dissolved in the petroleum hydrocarbon to form the gel. This latter procedure is not preferred, however, since the unvulcanized rubber is much easier to dissolve in the petroleum hydrocarbon and it is also much easier to uniformly disperse the vulcanization agent or agents in the gel of unvulcanized rubber and petroleum hydrocarbon.

When preparing a gelatinous dynamite composition in accordance with the invention it is preferred to employ the process used in Example 3. However, the order of addition of the ingredients may be varied as desired to adapt the general process to different compositions and apparatus. Gelatinous explosive masses of non-explosive gel and a thermally stable crystalline high explosive, such as that shown in Example 2, may also be manufactured by preparing a gelatinous composition of the crystalline explosive and an unvulcanized butyl rubber-petroleum hydrocarbon gel, dispersing vulcanizing agent therein, and subsequently vulcanizing the butyl rubber in situ. For example, cyclonite is thermally stable even at temperatures as high as 200 C. If vulcanizing agents are chosen, therefore, which will effect the desired cross-linking at temperatures safely below 200 C., in situ vulcanization may be safely accomplished. However, even aside from the normal safety factors, such a procedure involves heating of much larger masses of material and would not normally be preferred. This procedure would not be desirable when liquid nitric explosive esters and other less thermally stable explosive is. used.

In gelatinous dynamites according to the invention, single liquid, explosive nitric esters or mixtures thereof may be employed. The crystalline high explosive materials which may be employed include ammonium nitrate, cyclonite, pentaerythritol tetranitrate, diethanoldinitramine and the like.

The necessary vulcanizing temperatures employed will vary with the vulcanizing agents, promoters, and accelerators employed and the specific temperatures are known to the art. In general, it has been found sufficient to gradually heat the rubber and vulcanizing agents from room temperature to about C. This practice will not detrimentally affect the butyl rubbers or the finished compositions incorporating the rubbers even though some of the accelerators, activators and promoters which may be employed may decompose below 170 C. The desired cross-linking has been found to take place during the course of raising the temperature to 170 C. In fact, it may be desirable in some instances that the unusued crosslinking agent and the accelerators, activators, and promoters used be decomposed.

The conventional vulcanizing agents, promoters, activators and accelerators are operable in forming nonexplosive gels in accordance with the invention. As the basic vulcanizing or cross-linking agent it is preferred to employ sulfur or a compound containing available sulfur such as the alkyl-substituted thiuram disulfides, or compounds containing available oxygen such as the peroxides and hydroperoxides. The combination of Example 1 of sulfur as the vulcanizing agent and tetramethyl thiuram disulfide as a promoter is preferred.

As already indicated, butyl rubbers may be prepared and are commercially available in many different degrees of polymerization. However, the words vulcanized and vulcanization as used in the specification and claims are to be distinguished from the broader terms of polymerized and polymerization. The results obtained by the present invention are obtained substantially entirely by the cross-linking of molecules of butyl rubber which already have a given degree of polymerization. By the present invention, the increased viscosity of a given gel is obtained through the conversion of a normally linear, polymeric structure to a three-dimensional structure. The gels of the invention, therefore, are basically different from the gel in which the butyl rubber has not been vulcanized or cross-linked. In the case of an unvulcanized butyl rubber, the gel results from solubility of constituents of the rubber in the particular solvent. The higher the degree of polymerization of the butyl rubber, the more dimcult it becomes to get the rubber into solution. When the given rubber is vulcanized and especially when vulcanized in situ in the petroleum hydrocarbon according the preferred procedure, the increased viscosity clearly is directly attributable to the increased size of the cross-linked molecule. However, the viscosity increase is not accompanied by leakiness of the gel, but instead the gel becomes more rubbery and better consolidated. This clearly indicates that the structure of the gel rests on some-thing more than just the solubility of the crosslinked polymer in the petroleum hydrocarbon.

The compositions and process of the invention have many advantages. By employing the nonexplosive gels in nitroglycerin dynamites, less of the expensive, difficultly workable nitrocellulose-nitroglycerin gel need be used to obtain desirable physical characteristics. Furthermore, the combination of the two gels gives improved water resistance, consistency and uniformity. Since the liquid explosive nitric ester content is substantially lowered, less absorbent carbonaceous material is needed. Therefore, additional oxygen carrying salts such as ammonium nitrate can be employed to maintain the original percentage. weight strength of the dynamite. At the same time, the addition of the nonexplosive gel having a high negative oxygen balance makes up for the loss of the absorbent ingredients. The nonexplosive gels of the invention are, furthermore, excellent water-resistant binders for dry powdered explosive such as ammonium nitrate and as binders for such highly powerful crystalline explosives as cyclonite and pentaerythritol tetranitrate. The vulcanized butyl rubber gels are particularly attractive due to their relative economy as compared to gels prepared from other synthetic rubbers and natural rubber.

What I claim and desire to protect by Letters Patent is:

1. A detonative, gelatinous explosive composition comprising high explosive material of the group consisting of liquid explosive nitric esters, nitrocellulose, nitrostarch and crystalline high explosives; and from about 1 to about of a nonexplosive gel containing (1) at least one substantially nonvolatile, water-insoluble petroleum hydrocarbon of the group consisting of petrolatum, parafiin base oils, naphthene base oils, intermediate base oils, cylinder oil, and bright stock, and (2) a vulcanized copolymer of isobutylene and isoprene.

2. A gelatinous explosive composition according to claim 1 in which the nonexplosive gel contains between 5 and 20% by weight of the vulcanized copolymer of isobutylene and isoprene.

3. A gelatinous explosive composition according to claim 1 in which the nonexplosive gel contains between 5 and 20% by Weight of a sulfur vulcanized copolymer of isobutylene and isoprene.

4. A gelatinous explosive composition according to claim 1 in which the nonexplosive gel contains between 5 and 20% by weight of an oxygen vulcanized copolymer of isobutylene and isoprene.

5. A detonative, gelatinous explosive composition comprising high explosive material of the group consisting of liquid explosive nitric esters, nitrocellulose, nitrostarch and crystalline high explosives; and from about 1 to about 10% of a nonexplosive gel containing (1) at least one substantially nonvolatile, water-insoluble petroleum hydrocarbon of the group consisting of petrolatum, parafiin base oils, naphthene base oils, intermediate base oils, cylinder oil, and bright stock, and (2) a sulfur vulcanized copolymer of isobutylene and isoprene, said nonexplosive gel containing between 5 and 20% by weight of the copolymer, and said copolymer having prior to vulcanization, an ML viscosity at 212 F. at 8 minutes of above 40.

6. A detonative, gelatinous explosive composition comprising high explosive material of the group consisting of liquid explosive nitric esters, nitrocellulose, nitrostarch and crystalline high explosives; and from about 1 to about 10% of a nonexplosive gel containing (1) at least one substantially nonvolatile, water-insoluble petroleum hydrocarbon of the group consisting of petrolatum, paraflin base oils, naphthene base oils, intermediate base oils, cylinder oil, and bright stock, and (2) an oxygen vulcanized copolymer of isobutylene and isoprene, said nonexplosive gel containing between 5 and 20% by weight of the copolymer, and said copolymer having prior to vulcanization, an ML viscosity at 212 F. at 8 minutes of above 40.

7. A process for preparing high strength detonative gelatinous explosive compositions which comprises dissolving a copolymer of isobutylene and isoprene in a substantially nonvolatile, water-insoluble petroleum hydrocarbon of the group consisting of petrolatum, paraflin base oils, naphthene base oils, intermediate base oils, cylinder oil and bright stock; dispersing a vulcanizing agent in the resulting solution, heating the solution at a vulcanizing temperature until thickening is obtained, cooling the resulting nonexplosive gel and admixing high explosive material with the gel to form a gelatinous explosive containing between 1 and 10% of the nonexplosive gel.

8. A process for preparing a gelatinous high explosive which comprises dissolving a copolymer of isobutylene and isoprene in a substantially nonvolatile, water-insoluble petroleum hydrocarbon of the group consisting of petrolatum, paraffin base oils, naphthene base oils, intermediate base oils, cylinder oil and bright stock; dispersing a vulcanizing agent in the resulting solution, heating the solution at a vulcanizing temperature until thickening is obtained, cooling the resulting nonexplosive gel and admixing particulate, crystalline secondary high explosive with the gel to form a composition containing between 1 and 10% of the nonexplosive gel.

9. A process for preparing a gelatinous dynamite which comprises admixing liquid, explosive nitric ester with nitrocellulose to form an explosive gel, dissolving a copolymer of isobutylene and isoprene in a substantially nonvolatile, water-insoluble petroleum hydrocarbon of the group consisting of petrolatum, paraffin base oils, naphthene base oils, intermediate base oils, cylinder oil and bright stock; dispersing a vulcanizing agent in the resulting solution, heating the solution at a vulcanizing temperature until thickening is obtained, cooling the resulting nonexplosive gel, combining the explosive gel, the nonexplosive gel and dope ingredients in such proportions that the nonexplosive gel comprises from 1 to 10% of the combination, and mixing the combination until a uniform gelatinous dynamite is obtained.

No references cited.

Claims (2)

1. A DETONATIVE, GELATINOUS EXPLOSIVE COMPOSITION COMPRISING HIGH EXPLOSIVE MATERIAL OF THE GROUP CONSISTING OF LIQUID EXPLOSIVE NITRIC ESTERS, NITROCELLULOSE, NITROSTARCH AND CRYSTALLINE HIGH EXPLOSIVES; AND FROM ABOUT 1 TO ABOUT 10% OF A NONEXPLOSIVE GEL CONTAINING (1) AT LEAST ONE SUBSTANTIALLY NONVOLATILE, WATER-INSOLUBLE PETROLEUM HYDROCARBON OF THE GROUP CONSISTING OF PETROLEUM PARAFFIN BASE OILS, NAPHTHENE BASE OILS, INTERMEDIATE BASE OILS, CYLINDER OIL, AND BRIGHT STOCK, AND (2) A VULCANIZED COPOLYMER OF ISOBUTYLENE AND ISOPRENE.

7. A PROCESS FOR PREPARING HIGH STRENGTH DETONATIVE GELATINOUS EXPLOSIVE COMPOSITIONS WHICH COMPRISES DISSOLVING A COPOLYMER OF ISOBUTYLENE AND IOSPRENE IN A SUBSTANTIALLY NONVOLATILE, WATER-INSOLUBLE PETROLEUM HYDRO CARBON OF THE GROUP CONSISTING OF PETROLEUM, PARAFFIN BASE OILS, NAPHHENE BASE OILS, INTERMEDIATE BASE OILS, CYLINDER OIL AND BRIGHT STOCK; DISPERSING A VULCANIZING AGENT IN THE RESULTING SOLUTION, HEATING THE SOLUTION AT A VULCANIZING TEMPERATURE UNTIL THICKENING IS OBTAINED, COOLING THE RESULTING NONEXPLOSIVE GEL AND ADMIXING HIGH EXPLOSIVE MATERIAL WITH THE GEL TO FORM A GELATINOUS EXPLOSIVE CONTAINING BETWEEN 1 AND 10% OF THE NONEXPLOSIVE GEL.