Abstract: The invention relates to composite particles, comprising a carrier particle and an at least partial surface coating, the carrier particle comprising a quartz and a layered silicate and the surface of the composite particle having at least one hydrophilic region and at least one hydrophobic region. The invention also relates to a method for producing composite particles, comprising the steps: a) providing carrier particles, comprising a quartz and a layered silicate, b) introducing the carrier particles into a mixing device, c) charging the carrier particles with a coating composition, d) coating the carrier particles with the coating composition by mixing the carrier particles with the coating composition, with the introduction of shear energy, e) subjecting the coated carrier particles to temperature. In addition, the invention relates to a mineral cast part or to a composite workpiece which comprises the above-described composite particles.

Abstract: The invention relates to composite particles, comprising a carrier particle and an at least partial surface coating, the carrier particle comprising a quartz and a layered silicate and the surface of the composite particle having at least one hydrophilic region and at least one hydrophobic region. The invention also relates to a method for producing composite particles, comprising the steps: a) providing carrier particles, comprising a quartz and a layered silicate, b) introducing the carrier particles into a mixing device, c) charging the carrier particles with a coating composition, d) coating the carrier particles with the coating composition by mixing the carrier particles with the coating composition, with the introduction of shear energy, e) subjecting the coated carrier particles to temperature. In addition, the invention relates to a mineral cast part or to a composite workpiece which comprises the above-described composite particles.

Abstract: The invention relates to a method for producing a coloured sand composition containing a large number of silica sand grains with outer coatings of colour pigments, wherein the method comprises the following steps: mixing caustic soda and water in a predetermined ratio, preferably of 1:2, to form a dilute caustic soda; mixing boric acid in a predetermined concentration with the dilute caustic soda to form a boric acid/caustic soda solution; mixing a binder with the boric acid/caustic soda solution in a predetermined ratio to form a coating mixture; coating the silica sand grains coated with the colour pigments with the coating mixture by adding the coating mixture to the silica sand grains, and indirectly heating the silica sand grains coated with the coating mixture in a system which is spatially sealed from the heating source by means of separate chambers for the heating process and the heating source. A coloured sand composition is also described.

Abstract: The invention relates to a method for producing a coloured sand composition containing a large number of silica sand grains with outer coatings of colour pigments, wherein the method comprises the following steps: mixing caustic soda and water in a predetermined ratio, preferably of 1:2, to form a dilute caustic soda; mixing boric acid in a predetermined concentration with the dilute caustic soda to form a boric acid/caustic soda solution; mixing a binder with the boric acid/caustic soda solution in a predetermined ratio to form a coating mixture; coating the silica sand grains coated with the colour pigments with the coating mixture by adding the coating mixture to the silica sand grains, and indirectly heating the silica sand grains coated with the coating mixture in a system which is spatially sealed from the heating source by means of separate chambers for the heating process and the heating source. A coloured sand composition is also described.