| abstract |
In a process for preparing copolymers through bulk polymerisation, from monomer mixtures made up of: (m1) 50 to 90 wt.% of alkylmethacrylate having 1 to 6 carbon atoms in the ester group, (m2) 5 to 25 wt.% of at least one vinyl aromatic substance, (m3) 1 to 25 wt.% of of maleic acid anhydride, as well as optionally (m4) O to 5 wt.% of alkylacrylate having 1 to 6 carbon atoms in the ester group, the sum of the monomer units (m1), (m2), (m3) and, optionally, (m4) being 100 wt.%, in the presence of polymerisation initiators and molecular weight regulators, the maleic acid anhydride (m3) is added, in the liquid state, to the other monomers before polymerisation. Preferably, in a first stage before polymerisation, mixtures of monomer units (m1) / (m3) are prepared in weight ratios of between 75/1 and 75/25 which are added in a second stage to the other monomer units (m2) and, optionally (m4). Methylmethacrylate is preferred as monomercomponent (m1) and styrene and/or alpha -methyl-styrene is preferred as monomer component (m2). |