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

Abstract

Process for preparing ultrafine powders based on polyamides by contacting polyamides having a relative solution viscosity η rel 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 suspended therein 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; the resulting ultrafine polyamide powders have a specific BET surface area of 5-100 m 2 /g; a fineness d 50 of less than 70 μm; an apparent density AD 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; which powders are equally suitable for coatings and for mouldings and components with improved mechanical properties.

1 . An ultrafine powder based on a polyamide, obtainable by contacting the polyamide having a relative solution viscosity η rel  in a range from 1.5 to 2.0, measured in a 0.5% m-cresol solution at 25° C., with a suspension of inorganic particles in an alcoholic medium 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, wherein a specific BET surface area is in a range of 5-100 m 2 /g; a fineness d 50  is less than 70 μm; an apparent density AD is in a range from 250 to 1000 g/l; and a particle content is from 0.1 to 80% by weight of the inorganic particles based on the total weight of the polyamide powder. 
     
     
         2 . A coating composition comprising the ultrafine powder based on the polyamides according to  claim 1 . 
     
     
         3 . A moulding comprising the ultrafine powder based on the polyamides according to  claim 1 . 
     
     
         4 . A method for producing the moulding of  claim 3 , comprising an injection extrusion or blow of the moulding. 
     
     
         5 . A method for producing the moulding of  claim 3 , comprising producing a granule and subsequent thermoplastic, and further injecting, extruding or blowing the moulding. 
     
     
         6 . The ultrafine powder according to  claim 1 , wherein the suspension of the inorganic particles is at least one selected from the group consisting of Al 2 O 3 , TiO 2 , ZrO 2 , SiO 2 , ZnO, Bi 2 O 3 , CeO 2 , ITO, ATO, IZO, boron nitride, boron carbide, mixed oxides and spinels, suspended in the alcoholic medium. 
     
     
         7 . The ultrafine powder according to  claim 1 , wherein the suspension of the inorganic particles is at least one of Al 2 O 3 . 
     
     
         8 . The ultrafine powder according to  claim 1 , wherein the specific BET surface area in a range of 10-25 m 2 /g. 
     
     
         9 . The ultrafine powder according to  claim 1 , wherein the apparent density AD in a range from 250 to 800 g/l. 
     
     
         10 . The ultrafine powder according to  claim 1 , wherein the particle content is from 1 to 60% by weight of the inorganic particles based on the total weight of the polyamide powder. 
     
     
         11 . The process according to  claim 1 , wherein the apparent density AD in a range from 300 to 500 g/l.