Semi-continuous method for emulsion polymerisation

A process for preparing aqueous polymer dispersions by means of radically initiated emulsion polymerization, in aqueous medium, of vinyl ester and ethylene and optionally further ethylenically unsaturated comonomers, in polymerization reactors in series, wherein

• in a first, discontinuous polymerization phase, the reactants for the polymerization are included at least in part in an initial charge to the first polymerization reactor and the remainder is metered in, the polymerization being performed under a pressure p of 5 to 120 bar abs. and at a temperature T of 20° C. to 120° C.,
• and with a degree of reactor filling of greater than 90% by volume and at a conversion of at least 90% by weight of the monomers used up until that point, in a second, continuous polymerization phase, the reactants are supplied continuously to the first polymerization reactor and product is withdrawn continuously from the first polymerization reactor, and the product is transferred continuously into a second polymerization reactor, and from this time point on, metering of reactant and withdrawal of product in the first polymerization reactor are controlled such that these amounts correspond to one another, and in the second polymerization reactor the polymerization is continued under a pressure p of < 5 bar abs. through to a conversion of at least 98% by weight of the monomers used, based on the total weight of the amount of monomer used in the process.