Process for the preparation of a graft copolymer latex of core/shell dispersion particles having improved phase binding between core and shell

A process for the preparation of a graft copolymer latex of core/shell dispersion particles having improved phase binding between core and shell in a twostage emulsion polymerization process, a latex based on one or more monomers selected from the group consisting of (meth)acrylates of alcohols having 1 to 14 C atoms, vinyl esters of saturated aliphatic carboxylic acids having 1 to 14 C atoms, olefins, vinyl aromatics, vinyl halides and vinyl ethers being prepared in the first stage, wherein

• a) hydrogen peroxide and a free radical initiator which decomposes into free radicals with a half-life of >48 hours at the temperature of the latex at the time of addition of the hydrogen peroxide are added to the polymer latex of the first stage simultaneously or in any order and
• b) in the second stage, this mixture is heated to a temperature at which the free radical initiator decomposes into free radicals with a half-life of <48 hours and/or a reducing agent is added and
• c) after the addition of the graft monomer phase which contains one or more ethylenically unsaturated monomers which form homopolymers having a glass transition temperature T.sub.g of >20.degree. C., the latex polymer is grafted, optionally with further reducing agent.