Process for producing ultrafine powders based on polyamides, ultrafine polyamide powders and their use

摘要

Process for preparing ultrafine powders based on polyamides by contacting polyamides having a relative solution viscosityηrel in the range from 1.5 to 2.0, measured in 0.5% m-cresol solution at 25° C., with an alcoholic medium in the presence of inorganic particles under the action of pressure and/or temperature to generate an at least partial solution, and then precipitating the polyamide from the at least partial solution, characterized in that a suspension of the inorganic particles suspended in the alcoholic medium is used. The resulting ultrafine polyamide powders have a specific BET surface area in the range of 5-100 m2/g; a fineness d50 of less than 70μm; an apparent density AD in the range from 250 to 1000 g/l; and a particle content of 0.1 to 80% by weight of inorganic particles based on the total weight of the polyamide powder. They are equally suitable for coatings and for moldings and components with improved mechanical properties.