Hoechst Aktiengesellschaft

Rudolf Wesselmann

Karl Kaiser

Alexander Ohorodnik

Bernhard Kuxdorf

Monomeric matter is removed from an aqueous dispersion of a polymer containing at least 50 weight % of polymerized vinyl chloride. To this end, the dispersion is introduced into the upper portion of a column provided with sieve plates and contacted therein for 10 seconds up to 20 minutes, under 600 up to 1200 mm Hg, with hot steam at 100.degree. up to 150.degree. C. flowing countercurrently with respect to the dispersion. The polymer dispersion so treated is removed from the column base portion; and a vaporous matter mixture issuing at the head of the column is condensed stagewise so as to recover an aqueous phase and the monomeric matter.

Process for continuously removing monomers from an aqueous dispersion of

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.degree. to 90.degree. 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 m.sup.3 per m.sup.2 of tray area per hour and contacted countercurrently with steam at 80.degree. to 150.degree. C., under 0.5 to 5 bars, and in a proportion of 30 to 100 kg of steam per m.sup.3 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.

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Rudolf Wesselmann