Particulate compositions of particulate metal and polymer binder

Abstract

A particulate composition wherein each particle thereof includes a first metal (e.g., tungsten), an optional second metal (e.g., tin), and a polymer binder (e.g., thermoplastic polyvinyl alcohol) is described. The first metal has a particle size of less than or equal to 10 μm, and the second metal has a particle size of less than or equal to 20 μm. The polymer binder is typically present in each particle of the particulate composition in an amount of from 0.5 to 2.5 percent by weight, based on the total weight of the particulate composition. The particulate composition has an average particle size of 25 to 300 μm, and is free flowing. The particles of the particulate composition are preferably substantially spherical. Also described is a method of preparing the particulate composition by means of spray drying. The particulate compositions may be used to prepare molded articles, such as frangible projectiles (e.g., frangible bullets).

Description

FIELD OF THE INVENTION [0001] The present invention relates to particulate compositions that include one or more particulate metals (e.g., tungsten and tin) and a thermoplastic and / or thermosetting polymer binder. Each particle of the particulate composition has substantially the same proportions of metal and polymer binder. The present invention also relates to a method of preparing such particulate compositions by means of spray drying, and to molded articles prepared from such particulate compositions (e.g., frangible projectiles). BACKGOUND OF THE INVENTION [0002] Frangible projectiles, such as frangible bullets, are designed to fragment upon impact with an object of sufficient density (e.g., a human being, an animal or a wall). Relative to standard non-frangible bullets, frangible bullets are capable of imparting increased tissue and internal organ damage (i.e., improved take-down capacity) while at the same time minimizing the risk of the bullet passing intact through an inten...

AI Technical Summary

Benefits of technology

[0011] zinc, iron, copper, aluminum, combinations thereof, and alloys of at least two me...

Problems solved by technology

However, there are environmental and health concerns associated with lead projectiles.

Lead projectiles left in the field (e.g., a marsh) can lead to increased lead levels in the ecosystem and the food chain.

The use of lead projectiles in indoor firing ranges raises health concerns associated with lead dust and vapors that may be formed when lead bullets hit the down range back wall.

However, maintaining two or more metal powders in a desired proportion prior to molding of the projectile can be problematic due to, for example, separation of the metals resulting from handling related vibrations.

However, there are typically handling and safety concerns associated with metal powders having small average particle sizes of, for example, less than 20 μm.

Metal powders of such small particle size may not flow properly when being fed into a projectile mold, and may clog the feed port thereof.

There may be increased explosion hazard and respiratory injury concerns associated with the use of small particle size metal powders in the production of molded articles there from, such as frangible projectiles.