Preparation of powders having spherical-shaped particles from io

Details Preparation of powders having spherical-shaped particles from io Preparation of powders having spherical-shaped particles from io

1973-11-28

1976-01-20

White, Robert F.

Plastic and nonmetallic article shaping or treating: processes

Formation of solid particulate material directly from molten...

Utilizing centrifugal force or rotating forming zone

264 15, B01J 218

Patent

active

039339548

ABSTRACT:
Method whereby spherical-shaped copolymer particles having a rough surface are produced. In a closed shear zone of a shear device under positive pressure water, at least 0.6% by weight of ammonia, and up to 50% by weight of copolymers of alpha-olefins and alpha, beta-ethylenically unsaturated carboxylic acids having from 3 to 8 carbon atoms, and optionally an additional monoethylenically unsaturated monomer, the copolymer having from 0% to 90% of the carboxylic acid groups ionized by neutralization with metal ions, are sheared at a temperature above the melting point but below the thermal degradation point of the copolymer to form a homogeneous aqueous slurry wherein the copolymer particles have an average particle size of less than 100 microns. The slurry is maintained with agitation at a temperature above the copolymer melting point for at least 0.5 minute until substantially all the copolymer particles become spherical. Agitation is continued and the slurry is cooled to a temperature below about the copolymer freezing point over a period of at least 0.3 minute while the pressure is maintained at sufficient level to keep the water in the liquid state. The pressure of the cooled slurry is reduced to atmospheric pressure and the copolymer particles are separated from the aqueous component of the slurry. The spherical-shaped particles have an average diameter of 10 to 100 microns and the surface thereof is covered with hemispherical shaped bumps about 0.1 micron in diameter. The particles form a free-flowing powder useful in preparing clear, protective, shatter-resistant coatings for glass, and protective coatings for metals and other materials.

REFERENCES:
patent: 3586654 (1971-06-01), Lerman et al.

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