method for the removal of monomers from a water bearing dispersion of polymers, and formed product, wholly or partially purified in this manner, consisting of a polymer.

摘要

An aqueous polymer dispersion containing approximately 1 to 60 weight % of solid polymer particles with an average size of 20 to 500 microns and 5000 to 15,000 ppm of monomer(s), is freed from monomeric material. More specifically, the aqueous dispersion is preheated to 60 DEG to 90 DEG C. and introduced continuously into an upper portion of a column accommodating a plurality of apertured trays disposed one above another of which each has at least one eccentric aqueous dispersion descent shaft. The aqueous dispersion is introduced at a rate of a 5 to 35 m3 per m2 of tray area per hour and contacted countercurrently with steam at 80 DEG to 150 DEG C., under 0.5 to 5 bars, and in a proportion of 30 to 100 kg of steam per m3 of dispersion, for a mean period of 1 to 30 minutes; the pressure drop for steam ascending through one tray in the column being lower than that which would occur upon the undesirable passage of steam through one of the said shafts. At the column base, aqueous dispersion freed from monomeric material is removed and a vapor mixture emerging at an upper level of the column, is condensed, and monomeric material and an aqueous phase are recovered therefrom.