The invention relates to a composition, in particular a pulverulent master batch, comprising at least one nanoclay composed of a swellable inorganic layered material which has been modified by at least one siloxane component and by at least one non-anionic organic compound which has at least one aliphatic or cyclic radical having from 6 to 32 carbon atoms.The pulverulent master batch can result in a homogeneous mixture with a polymer powder and can be used as such. Also, a polymer master batch can be produced by compounding of the pulverulent master batch with a carrier polymer. The pulverulent master batch or the polymer master batch can be used as filler or in filler systems in various polymer compositions.