Polyvinyl acetals capable of forming emulsifier-free aqueous dispersions and redispersible dry powders, process for their manufacture and use

摘要

Polyvinyl acetals which are capable of forming emulsifier- and surfactant free aqueous dispersions and redispersible dry powders and contain copolymeric polyvinyl acetals containing amounts, sufficient to form a dispersion, on sulfo salt group-carrying comonomer units derived from copolymeric polyvinyl alcohols (PVALs) which contained sulfonate group-carrying comonomer units in the salt form are prepared by acetalation of the starting polyvinyl alcohols to be used by means of aldehydes or aldehyde acetals under acid-catalysed acetalation conditions in aqueous medium, giving emulsifier-free, stable, aqueous polyvinyl acetal dispersions from which dry, redispersible polyvinyl acetal powders can be obtained by spray drying or freeze drying. The novel polyvinyl acetals can be plasticised both in their aqueous dispersion form and in the dry powder form by mixing in plasticisers. The novel polyvinyl acetals can be employed both in the aqueous dispersion form and in the dry powder form in numerous areas of application in which polyvinyl acetals of the type known hitherto are usually already used. In addition, the advantageous property profile of novel polyvinyl acetals makes numerous new areas of application accessible.