Particulate compositions of particulate metal and polymer binder

a technology which is applied in the field of particulate metal and polymer binder, can solve the problems of increased lead levels in the ecosystem and food chain, difficulty in maintaining two or more metal powders in a desired proportion prior to the molding of the projectile, and insufficient flow of metal powders of such small particle siz

Inactive Publication Date: 2006-02-09
H C STARCK INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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 m...

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example a

Preparation of Particulate Metal Mixture

[0076] A particulate metal mixture was prepared by mixing 5443 grams of particulate tungsten (having an average particle size of 5 μm), and 1361 grams of particulate tin (having an average particle size of 12 μm) in a TURBULA shaker-mixer (available commercially from Glenn Mills, Inc.). The particulate tungsten and tin were mixed in the mixer for 20 minutes, and the resulting particulate metal mixture was determined to be substantially homogenously mixed by means of visual inspection. The particulate metal mixture of tungsten and tin was substantially dry and free flowing.

[0077] The average particle sizes of the particulate tungsten and particulate tin, from which the particulate metal mixture was prepared, were each determined in accordance with ASTM B 822. The particulate tungsten was obtained commercially from H.C. Stark Inc., and the particulate tin was obtained commercially from OMG Americas Inc.

example b

Preparation of Slurry

[0078] A slurry was prepared by mixing 5 grams of Antifoam 221 silicone-glycol emulsion (obtained commercially from Dow Corning Corporation) with 1270 grams of water, and then 91 grams of polyvinyl alcohol was added to the mixture of water and defoamer. The mixture of water, polyvinyl alcohol and defoamer was thoroughly mixed with an impeller. Next, 6803 grams of the particulate metal mixture of Example A was added to the mixture of water, polyvinyl alcohol and defoamer to form the slurry, which was continuously mixed using an impeller.

example c

Preparation of the Particulate Composition

[0079] The slurry of Example B, while continually being stirred with an impeller, was passed through a spray drier comprising a dual-fluid nozzle, at a rate of 907 grams / min. The spray drier was operated at an inlet temperature of 260° C. and an outlet temperature of 149° C.

[0080] The particulate composition resulting from the spray drying operation had: an average particle size of 75 μm (as determined in accordance with ASTM B 214); a Hall flow of less than 25 seconds / 50 g (as determined in accordance with ASTM B 213); and an apparent density of approximately 4 g / cm3 (as determined in accordance with ASTM B 329).

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PUM

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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...

Claims

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Application Information

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IPC IPC(8): F42B12/22
CPCF42B12/76F42B12/74
Inventor KOLB, CHRISTOPHER W.SPIRKO, JOSEPH R.OHM, SCOTT
Owner H C STARCK INC
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