the invention relates to thermoplastic polymer compositions in the form of masterbatches , comprising a matrix of an olefinic copolymer obtained from olefinic monomers and at least one alkylacrylate monomer , in which exfoliable organophilefilelrs of the lamellar type are dispersed , such as silicates , characterized in that after complete dispersion , the fillers are of nanometer scale with a content of at least 20 % by weight with relation to the composition . the invention is further of application for the production of polymeric materials particularly of the polyethylene type , with fillers , the thermomechanical and barrier properties of which are improved .