Encapsulated iron oxide particles having a needle shape, useful as a component e.g. for rubber mixtures, polymer preparations, comprises a core containing magnemite and magnetite, and a shell containing a metal oxide or metalloid oxide

Encapsulated iron oxide particles having a needle shape, comprises a core containing magnemite and magnetite, and a shell containing a metal oxide or metalloid oxide. Independent claims are included for: (1) the preparation of encapsulated iron oxide particles comprising introducing an aerosol comprising needle-shaped iron oxide particles and optionally shell material particles to reaction in a high temperature zone in a reducing gas atmosphere, and subsequently contacting the obtained material mixture with a quantity of gas comprising oxygen, preferably air sufficient for completely oxidizing the material mixture, optionally adding many shell material outlet compounds to the high temperature zone, and subsequently cooling the material mixture and separating the solids, provided that the shell particle in the aerosol and/or shell particle outlet compounds are used, where the sum of the shell particle and shell particle outlet compounds calculated as metal oxide or metalloid oxide, corresponds to the amount of metal oxide or metalloid oxide in encapsulated iron oxide particles, preferably hematite; or reacting by ignition an aerosol comprising a substance mixture of needle-shaped iron oxide particles and optionally shell material particles, an oxygen-containing gas and excess hydrogen-containing fuel gas, feeding a material mixture comprising excess oxygen-containing gas and reacting in a flame, optionally adding one or more shell material outlet compounds with the proviso that the shell particle in the aerosol and/or shell particle outlet compounds are used, where the sum of the shell particle and shell particle outlet compounds calculated as metal oxide or metalloid oxide, corresponds to the amount of metal oxide or metalloid oxide in encapsulated iron oxide particles, preferably hematite, cooling the material mixture and separating the material mixture; and (2) a silicone rubber comprising encapsulated iron oxide particles. Umhüllte Eisenoxidpartikel, die nadelförmig sind, einen Maghemit und Magnetit umfassenden Kern und eine ein Metalloxid oder Metalloidoxid umfassende Hülle aufweisen. Sie werden hergestellt, indem man in einer Hochtemperaturzone nadelförmige FeOOH-Partikel und gegebenenfalls Hüllstoffpartikel enthaltendes Aerosol in einer reduzierenden Gasatmosphäre zur Reaktion bringt, und nachfolgend das erhaltene Stoffgemisch mit einer Menge eines sauerstoffenthaltenden Gases in Kontakt bringt, die ausreicht das Stoffgemisch vollständig zu oxidieren