Polyvinyl acetals which can form emulsifier-free aqueous dispersions and redispersible dry powders, processes for their preparation and their use

摘要

Preparation of polyvinyl acetals which can form emulsifier- and surfactant-free aqueous dispersions and redispersible dry powders and contain copolymeric polyvinyl acetals with, in amounts sufficient to form a dispersion, comonomer units carrying sulfo salt groups which are derived from copolymeric polyvinyl alcohol (PVALs) which contained comonomer units carrying sulfonate groups in the salt form. The preparation is carried out by acetalization of the starting polyvinyl alcohols to be used with aldehydes or aldehyde acetals under acid-catalyzed acetalization conditions in an aqueous medium, emulsifier-free stable aqueous polyvinyl acetal dispersions being obtained, from which dry redispersible polyvinyl acetal powders can be obtained by spray drying or freeze drying. The polyvinyl acetals according to the invention can be plasticized by mixing in plasticizers both in their aqueous dispersion form and in the dry powder form. The polyvinyl acetals according to the invention can be employed, both in the aqueous dispersion form and in the dry powder form, in numerous fields of use where polyvinyl acetals of the type known to date are already usually used. Moreover, because of the advantageous spectrum of properties of polyvinyl acetals according to the invention, numerous new fields of use are accessible.