Inorganic filler material with retention properties, and method and use of such material

A method for producing a finely divided inorganic filler comprising composite filler particles made of macro-filler particles and micro-filler particles;

• and wherein the composite filler particle has a mean particle size between 0.3 and 12 micrometers;
• comprising the steps of
• providing macro-filler particles and micro-filler particles wherein the macro-filler particles are larger than the micro-filler particles and have a lower melting point, the macro-filler particles consist of glass and have a mean particle size between 0.2 and 10 micrometers, and the micro-filler particles consist of a nitride, carbide or oxide of one of the elements silicon, zirconium or aluminum and have a mean particle size between 0.01 and 1.5 micrometers;
• mixing the macro-filler particles and the micro-filler particles to produce an intimate mixture thereof;
• sintering the mixture to secure the micro-filler particles to the surface of the macro-filler particles to form a sintered product;
• dispersing the sintered product in a liquid using ultrasonic waves;
• allowing coarser sintered product particles to settle from the dispersion;
• and
• centrifuging the dispersion to recover the finely divided inorganic filler.