Abstract: The invention concerns redispersible polymer powders which can be used in a variety of ways, for example, in hydraulically binding systems, but also as binder in greatly varied applications and which can be produced by spray-drying of aqueous dispersions. The sprayable aqueous dispersions are prepared by mixing an aqueous polymer dispersion 1 (containing polymer I) with an aqueous polymer dispersion 2 (containing polymer II) where the diameters of the particles of polymer I are greater by a factor of 5 to 150, preferably 15 to 50, than the diameter of the particles of polymer II, and polymer I is a polymer which forms films at room temperature, while polymer II has a glass transition temperature which is higher than that of polymer I, is insoluble in water and thus it is present in the undissolved form in the aqueous dispersion to be sprayed. The polymer powders according to the invention excel by a clearly improved resistance to blocking and very good storage stability.

Abstract: The invention concerns well dispersible powders on the basis of carboxylated copolymers containing butadiene made of styrene and/or acrylonitrile, whose films taken from redispersion show good tensile strength. According to the invention, the latices are sprayed with mixtures of spraying aids consisting of 1 to 15 weight % of a salt of the alkylated di-phenyl-ether-di-sulphonic acid, caseinate and/or N-alkyl sulphosuccinamide and/or with 1 to 20 weight % of a di- or tetra sodium or potassium salt of an addition product from N-alkyl sulphosuccinamates with maleic acid mixed together with polyvinyl alcohol. The dispersions can be used especially in the construction industry and they offer an alternative to copolymers on the basis of polyvinyl acetates and acrylates.