Patent ID: 8013062

Claim:
A process for the preparation of a transparent and impact-resistant polymer material comprising a brittle matrix (I) having a glass transition temperature of greater than 0° C. in which is dispersed a block copolymer (II) of formula B-(A) n , n being between 2 and 20, with a polydispersity of between 1.5 and 3, B being a polymer block with a glass transition temperature of less than 0° C. and with a polydispersity index of less than 2 and A being a polymer block with a glass transition temperature of greater than 0° C., A being compatible with the matrix, wherein the block copolymer (II) is obtained by controlled radical polymerization in the presence of a nitroxide, comprising (1) preparing the first block B by mixing the monomer(s) with an alkoxyamine of formula: where R′ and R, which are identical or different, optionally connected so as to form a ring, are alkyl groups having between 1 and 40 carbon atoms optionally substituted by hydroxyl, alkoxy or amino groups; where R L is a monovalent group with a molar mass of greater than 16 g/mol; and where Z is a polyvalent radical carrying end functional groups of styrol or acryloyl, adding a nitroxide, and carrying out the polymerization at temperatures ranging from 60 to 250° C., pressures ranging from 0.100 bar to 80 bar, (2) diluting the first block B obtained in the mixture of monomers intended to form the block A compatible to the brittle matrix which is desired to see reinforced against impact, adding between 0 and 100 molar equivalents of a radical polymerization initiator, carrying out the polymerization at temperatures ranging from 60 to 250° C., and pressures ranging from 0.100 bar to 80 bar, the conversion of the monomer being from 10 to 100%, and separating the polymer obtained from the residual monomers by evaporation under vacuum at temperatures ranging up to 250° C., (3) mixing the product obtained in step (2) with the brittle matrix which it is desired to see reinforced against impact, optionally in the presence of other additives, and wherein the relative lengths of the first block B and the block A are selected such that n*Mn(A)/(n*Mn(A)+Mn(B)) is between 0.5 and 0.95, wherein, Mn(A) is the number-average molecular mass of the block A, Mn(B) is the number-average molecular mass of the first block B, and n is the number of polymer blocks A in the block copolymer obtained in step (2).