A process for the preparation of a mineral filler product, the process comprising the steps of: a) providing a calcium carbonate-containing material; b) providing water; c) providing at least one grinding agent; d) wet grinding the calcium carbonate-containing material in a mixture obtained by contacting in any order: i) the calcium carbonate-containing material provided in step a), with ii) the water provided in step b), and with iii) the at least one grinding agent provided in step c) in any order in at least one grinding unit to obtain a wet ground mineral filler; e) optionally classifying the wet ground mineral filler of step d) to obtain a coarse fraction and a fine fraction, wherein the coarse fraction is removed or subjected to wet grinding step d) and the fine fraction represents a fine mineral filler; f) drying the wet ground mineral filler of step d) and/or the fine mineral filler of step e) to obtain a dried mineral filler having a total moisture content of less than or equal to 1.0 wt.-%, based on the total weight of said dried mineral filler; and g) treating the dried mineral filler of step f) with a hydrophobizing agent to obtain a surface-treated product having a treatment layer on at least part of the surface of said product, wherein the hydrophobizing agent is selected from the group consisting of fatty acids having from 6 to 24 chain carbon atoms, mono-substituted succinic anhydrides, alkyl phosphoric acid esters, polyhydrogensiloxane, polydimethylsiloxane, and mixtures thereof; wherein the total moisture content in the mixture of step d) ranges from 15.0 to 50.0 wt.-%, based on the total weight of said mixture; the amount of the at least one grinding agent provided in step c) ranges from 0.01 to 10.0 wt.-%, based on the total dry weight of the calcium carbonate-containing material; the temperature in step d) ranges from 60 °C to 150 °C; and the at least one grinding agent is selected from the group consisting of styrene-maleic anhydride co-polymers and derivatives of styrene-maleic anhydride co-polymers, said derivatives being selected from styrene-maleic anhydride co-polymers having partially or fully hydrolyzed maleic anhydride units, wherein said grinding agent has a monomer unit ratio (styrene units: maleic anhydride units, S:MA) of from 1:2 to 5:1 and a molecular weight M w of from 500 to 40'000 g/mol. a) providing a calcium carbonate-containing material; b) providing water; c) providing at least one grinding agent; d) wet grinding the calcium carbonate-containing material in a mixture obtained by contacting in any order: i) the calcium carbonate-containing material provided in step a), with ii) the water provided in step b), and with iii) the at least one grinding agent provided in step c) in any order in at least one grinding unit to obtain a wet ground mineral filler; i) the calcium carbonate-containing material provided in step a), with ii) the water provided in step b), and with iii) the at least one grinding agent provided in step c) in any order in at least one grinding unit to obtain a wet ground mineral filler; e) optionally classifying the wet ground mineral filler of step d) to obtain a coarse fraction and a fine fraction, wherein the coarse fraction is removed or subjected to wet grinding step d) and the fine fraction represents a fine mineral filler; f) drying the wet ground mineral filler of step d) and/or the fine mineral filler of step e) to obtain a dried mineral filler having a total moisture content of less than or equal to 1.0 wt.-%, based on the total weight of said dried mineral filler; and g) treating the dried mineral filler of step f) with a hydrophobizing agent to obtain a surface-treated product having a treatment layer on at least part of the surface of said product, wherein the hydrophobizing agent is selected from the group consisting of fatty acids having from 6 to 24 chain carbon atoms, mono-substituted succinic anhydrides, alkyl phosphoric acid esters, polyhydrogensiloxane, polydimethylsiloxane, and mixtures thereof;