Method for regenerating aqueous dispersions and cell package for electrodialysis

摘要

The present invention relates to a method for reducing the ionic strength or the concentration of certain polyvalent ions in aqueous dispersions of organic binding agents or inorganic solid bodies by electrodialysis, and a cell package suitable for use in the method. This method permits stabilization of aqueous compositions of the dispersed components by regulating the ionic strength or the concentration of certain polyvalent ions thereby increasing the durability and throughput times of coating baths. More particularly, the method is used in removing polyvalent metal cations from anionically stabilized aqueous binding agent dispersions. A special application exists in removing from autophoretic baths, which contain anionically dispersed organic binding agents and possibly inorganic pigments for forming protective layers on metallic components, polyvalent cations of zinc, iron and aluminum, which accumulate in the bath when components with surfaces comprised at least partially from zinc, iron and/or aluminum, are processed.

主权项

1. A cell pack for electrodialysis comprising:
a membrane stack consisting of a number n of membranes and n+1 membrane spacers of planar configuration each comprising a frame delimiting an internal space permeable to fluid in a direction orthogonal to a direction of the stack,wherein the n+1 membrane spacers and the n membranes are arranged alternately in the direction of the stack,wherein all of the membranes represent cation exchangers or all of the membranes represent anion exchangers, andwherein the membrane spacers comprise membrane spacers for laminar flow configured to have fluid-permeable internal space comprising a plurality of linear contact regions with each of the respective directly adjacent membranes, wherein the membrane spacers for laminar flow are not external spacers of the stack, wherein the linear contact regions are spaced apart from one another, wherein the linear contact regions formed with at least one of the directly adjacent membranes run in a same orientation as one another and do not cross one another, and an average distance of the linear contact regions from one another is no smaller than the spacing of the membranes that are separated from one another by the membrane spacers in a direction of their surface normals.