Continuous removal of monomers from an aqueous dispersion of a polymer

US4148990A · kind A · utility

Assignee

• Hoechst GmbH · DE

Inventors

• Bernhard Kuxdorf · Münstermaifeld, DE
• Karl Kaiser · Long Beach, US
• Rudolf Wesselmann · Lechenich, DE

Key dates

• Filing date: Sep 7, 1977
• Grant date: Apr 10, 1979
• Expiry date: Sep 7, 1997

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C08F6/16
• WIPO field: Chemical engineering
• WIPO sector: Chemistry

Abstract

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 r…