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A method of producing plastic-based casings including preformed metal fragments for ordnance articles, such as hand grenades, weapon-launched grenades or the like, by rotational molding in a shell-mold; a pulverulent thermoplastic polymer material, such as polyethylene, and steel fragments or partic

A method of producing plastic-based casings including preformed metal fragments for ordnance articles, such as hand grenades, weapon-launched grenades or the like, by rotational molding in a shell-mold; a pulverulent thermoplastic polymer material, such as polyethylene, and steel fragments or particles are introduced into the cold shell mold, optionally in the form of a pre-compact; the closed mold is rotated slowly, i.e. at a speed where the polymer and metal constituents tend to tumble about the inner mold surface and are not held substantially thereon by centrifugal effects; while continuously rotating the shell mold about two or more axes of rotation, the mold is heated by an externally applied hot fluid such as hot gas. As the temperature of the wall of the mold increases, an adhering layer of viscous polymer is formed thereon while the metal fragments continue to tumble; only when most of the polymer material is in a viscous molten state and has formed a layer covering the inner surface of the mold, the metal particles will adhere to the viscous material layer and form a metal particle monolayer thereon; then, the mold is cooled while still in rotation until the polymer solidifies. Finally, the molded product is discharged from the shell and provides an integral casing substantially consisting of an outer wall of polymer material and a monolayer of metal fragments adhering thereto. Molecular cross-linking of the polymer may be effected by a cross-linking agent and activating the latter after formation of the monolayer.

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1. A method of producing a fragmentation casing for an explosive ordnance article of the type having a charge substantially enclosed by a casing member for explosive disintegration thereof upon ignition of said charge, said casing having an integral structure combining a wall formed of an organic po

1. A method of producing a fragmentation casing for an explosive ordnance article of the type having a charge substantially enclosed by a casing member for explosive disintegration thereof upon ignition of said charge, said casing having an integral structure combining a wall formed of an organic polymer composition and a plurality of preformed metal fragments, said method comprising the steps of: (A) introducing a predetermined quantity of a normally solid polymer composition in the form of fine particles capable of coalescing and melting at an elevated temperature, and a predetermined quantity of said preformed metal fragments into a cold shell mold provided with a thermally conducting shell mold wall and having an interior surface shaped to substantially correspond with the outer shape of said casing; said predetermined quantity of said polymer composition being sufficient to form a continuous layer of said polymer composition in a molten form on said interior surface of said shell mold wall and said predetermined quantity of said metal fragments being sufficient to form a layer of said metal fragments on said continuous layer of said polymer composition; and said metal fragments having a mean particle size that is at least twice as large as the mean particle size of said fine particles of said polymer composition; (B) closing said shell mold containing said fine particles of said polymer composition and said metal fragments and slowly rotating said closed shell mold about at least two different axes of rotation; (C) externally heating said closed and revolving shell mold with a heated fluid having a temperature above that temperature which causes melting of said polymer composition; (D) continuing said heating of said revolving shell mold until a coherent and substantially uniform layer of said melted polymer composition has formed on said interior shell mold surface, said layer being covered on its inner surface with a layer of metal fragments adhering thereto; (E) cooling said revolving shell mold, and (F) discharging the casing formed in said mold. 2. The method of claim 1, wherein said polymer composition is capable of molecular cross-linking and wherein said layer formed in step (D) is subjected to cross-linking conditions. 3. The method of claim 2, wherein said polymer composition contains a cross-linking agent capable of controlled thermal activation, and wherein said polymer layer formed in step (D) is at least partially cross-linked by heating for thermal activation of said cross-linking agent prior to step (E). 4. The method of claim 1, wherein said polymer composition consists, at least in part, of a polyalkylene. 5. The method of claim 1, wherein said metal fragments have substantially granular shapes. 6. The method of claim 1, wherein said particles of said polymer composition have approximately spherical shapes and maximum particle dimensions of below about 1 mm. 7. The method of claim 1, wherein said metal fragments have a mean particle size in the range of from about 1 to about 5 mm. 8. The method of claim 1, wherein said coherent layer of said melted polymer composition formed in step (D) has a thickness that is at least as large as said mean particle size of said metal fragments. 9. The method of claim 8, wherein said coherent layer formed in step (D) has a thickness that is not more than twice as large as said mean diameter of said metal fragments. 10. The method of claim 3, wherein said cross-linking is effected by heating to a temperature and for a period sufficient to activate said cross-linking agent. 11. The method of claim 4, wherein said polymer composition consists, at least in part, of a catalytically cross-linkable polyalkylene. 12. The method of claim 11, wherein said polymer composition consists, at least in part, of a catalytically cross-linkable polyethylene. 13. The method of claim 5, wherein said metal fragments are made of steel. 14. The method of claim 6, wherein said particles of said polymer composition have maximum particle dimensions of not more than 500 μm. 15. The method of claim 7, wherein said metal fragments have a mean particle size in the range of from about 2 to about 3 mm.