A process is described for the preparation of water repellent materials made of acrylic fibre which comprises: (a) a first step in which the material is subjected to Plasma treatment in the presence of a reactive gas or a mixture thereof with a noble gas; and (b) a second step in which the material obtained in step (a) is subjected to waterproofing by means of (i) traditional resin finish or (ii) with Plasma generated in the presence of fluorinated compounds. The materials made of acrylic fibre thus obtained are characterized by a waterproofing degree higher than 25 cm of water column and have a rigid appearance or good draping and softness depending on whether they have been waterproofed with treatment (i) or (ii). These materials are used in the preparation of covers or sun shields.