Binder for paper coating compositions

A process for preparing a polymer dispersion, comprising radically initiated, aqueous emulsion polymerization, without the use of seed latex, in the presence of one or more emulsifiers and optionally protective colloids, of

• a) 50 to 93% by weight of at least one vinyl ester of an alkanoic acid with 1 to 12 C-atoms, whose homopolymer has a glass transition temperature Tg below about 350K (78° C.), according to ASTM D3418-82 at a heating rate of 10K (10° C.) per minute, taking the midpoint temperature as Tg,
• b) 2 to 30% by weight of ethylene,
• c) 5 to 20% by weight of at least one monomer whose homopolymer has a glass transition temperature Tg of at least about 350K (78° C.), according to ASTM D3418-82 at a heating rate of 10K (10° C.) per minute, taking the midpoint temperature as Tg,
• d) 0.1 to 2% by weight of ethylenically unsaturated silane monomers,
• e) 0 to 5% by weight of further ethylenically unsaturated monomers different from monomers c) or d) that are copolymerizable with vinyl acetate and ethylene,
• based in each case on the total weight of the monomers used for the polymerization, with the data in % by weight summing in each case to 100% by weight;
• wherein at least a part of the emulsifiers and/or protective colloids, and at least a part of the comonomers a), b), c), d) and e) is added initially, and the reaction mixture is heated and polymerization is initiated by metering initiator components, and the remaining part of the comonomers is added during polymerization.