A process for increasing the scratch resistance of a composition comprising a thermoplastic organic polymer and a scratch resistant polymer composition per se. The process for increasing the scratch resistance of a composition comprising a thermoplastic organic polymer (P) comprises reactively mixing a thermoplastic organic polymer (A) and an organopolysiloxane (B) in a first step (I) at a temperature at which the thermoplastic organic polymer (A) and the organopolysiloxane (B) are in liquid phases to form a masterbatch. The organopolysiloxane (B) contains at least one functionality capable of reacting with the thermoplastic organic polymer (A) so that a copolymer of components (A) and (B) is formed in the masterbatch during the reactive mixing. The process further comprises a second step (II) of mixing the masterbatch with the composition comprising the thermoplastic organic polymer (P).