The present invention relates to an earth alkali carbonate-containing filler material having a volatile onset temperature of ‰¥ 350 °C, which is at least partially surface modified by using at least one polyhydrogensiloxane for increasing the hydrophobicity and/or decreasing the moisture pick up, a process for preparing such a surface modified earth alkali carbonate-containing filler material, a fibre and/or filament and/or film and/or thread and/or breathable film comprising the surface modified earth alkali carbonate-containing filler material as well as an article comprising the surface modified earth alkali carbonate-containing filler material and/or the fibre and/or filament and/or film and/or thread and/or breathable film, preferably its use in polyester products.