Patent ID: 7388052

Claim:
A process for the preparation of a block copolymer by means of radicalic polymerization, which comprises: a) polymerizing a vinylaromatic monomer at a temperature higher than, or equal to, 120° C., in the presence of a radicalic initiating system, consisting of a compound having general formula (I): wherein R 1 and R 2 , the same or different, represent a methyl or ethyl radical, X 1 represents a hydrogen atom, X 2 represents a hydrogen atom or a hydroxyl, or X 1 and X 2 , the same or different, represent a C 1 -C 4 (iso)alkyl radical, or, they jointly form an aromatic ring, n is equal to zero or 1, and R 3 represents a radical selected from the group consisting of —C(CH 3 ) 2 —CN, —C(CH 3 ) 2 —Ph, and —CHCH 3 Ph; in a mixture with radical generator compounds (G) selected from the group consisting of peroxides, peresters, percarbonates, and azobisdialkyldinitriles, and with molar ratios I/G lower than 4; until a conversion of the monomer ranging from 5 to 99.9% is obtained; b) feeding to the polymerization mixture of step (a), after obtaining the desired conversion, methacrylonitrile in such a quantity that, at the end of the polymerization, the total weight of the block copolymer, Mw, is lower than 1,000,000, wherein step b) is carried out at the same operating temperature and in the presence of the same initiating system as step a); and c) recovering, at the end of the polymerization, the block copolymer thus obtained, wherein a precipitation and/or recovery step of a first polymeric block is absent between steps a) and b).