GB736956A - Improvements in the preparation of particulate highly polymeric materials in a form suitable for transport - Google Patents

Abstract

Bulky particulate highly polymeric organic materials are compressed at temperatures below their thermal softening temperatures into blocks having a density not exceeding 85 and preferably 75 per cent of the true density of the material, and skins are formed on the blocks by applying a small quantity of a solvent for the material to the surfaces of the blocks and then removing it. The density of the material prior to its compression is not more than half its true density. The material may be a cellulose ether or ester, such copolymers comprising vinyl chloride, vinylidene chloride, vinyl acetate or acrylonitrile as are soluble in acetone, and such high linear condensation polymers of the polyamide, polyurethane and polyester types as are soluble in alcohol. Before the particulate material is compressed it is preferably ground. The compression is preferably effected at atmospheric temperature, but a higher temperature may be used, provided that it is not so high that the individual particles of the material begin to stick together. The blocks formed by compression should preferably have rounded edges. The solvent applied to the surface of the block may be allowed to penetrate the block about 0.005 to 0.1 inch and may then be removed by evaporation. In the example, an acetone-soluble cellulose acetate of bulk density about 25 lb./cu. ft. is ground and compressed at room temperature in a cylindrical mould having rounded edges under a pressure of about 1.4 tons/sq. inch to an apparent density of about 50 lb./cu. ft. Acetone is then sprayed on to the surface of the block and rapidly removed by evaporation in a current of warm air. The process converts particulate materials into a form which is more suitable for transport, is easily broken down again for use, and is not unduly friable when handled.