Use as a rheological agent in a plastic loaded paste, a calcium carbonate dry milled with a copolymer of (meth) acrylic acid with an alkoxy or hydroxy polyalkylene glycol function.

The invention resides in the use, as an agent reducing the viscosity of a thermoplastic or thermosetting paste; loaded with a calcium carbonate, a calcium carbonate characterized in that it is obtained by dry milling a part, and in that it is dry milled in the presence of an aid agent grinding which is a copolymer of (meth) acrylic acid with a monomer having an alkoxy or hydroxy polyalkylene glycol function other. The invention also relates to thermoplastic and thermoset pastes loaded obtained.