The invention firstly concerns the use as a compatibilising agent, in a process to manufacture a chlorinated thermoplastic resin filled with a mineral material, of a comb polymer having at least one anionic monomer with ethylenic unsaturation, to which is grafted at least one polyalkylene oxide group. The invention also concerns the chlorinated thermoplastic materials thus obtained, which have an improved compatibility between the filler and the chlorinated thermoplastic resin, whilst reducing the quantity of compatibilising agents as used in the chlorinated and filled thermoplastic materials according to the prior art, where the said compatibilising agents used in the prior art were essentially fatty acids, and more specifically stearic acid or its salts.