REVERSE-PHASE POLYMERISATION PROCESS

A reverse-phase suspension polymerisation process for the manufacture of polymer beads comprising forming aqueous monomer beads comprising an aqueous solution of water-soluble ethylenically unsaturated monomer or monomer blend and polymerising the monomer or monomer blend, to form polymer beads while suspended in a non-aqueous liquid, and recovering polymer beads, in which the process comprises providing in a vessel (1) a volume (2) of non-aqueous liquid wherein the volume of non-aqueous liquid extends between at least one polymer bead discharge point (3) and at least one monomer feed point (4), feeding the aqueous monomer or monomer blend through orifices (5) into, or onto, the non-aqueous liquid to form aqueous monomer beads, allowing the aqueous monomer beads to flow towards the polymer bead discharge point initiating polymerisation of the aqueous monomer beads to form polymerising beads, wherein the polymerising beads form polymer beads when they reach the polymer bead discharge point, removing a suspension of the polymer beads in non-aqueous liquid from the vessel at the polymer bead discharge point and recovering, water soluble or water swellable polymer beads from the suspension, in which the aqueous monomer or monomer blend and/or the orifices is/are vibrated such that the frequency multiplied by the weight average droplet diameter is between 150 and 800 mm/s. The invention also relates to the apparatus suitable for carrying out a reverse-phase suspension polymerisation and polymer beads obtainable by the process or employing the apparatus. Furthermore, the invention also relates to polymer beads having a weight mean particle size in the range of 0.05 to 5 mm which are held in a container in an amount of at least 300 kg having a standard deviation of particle size less than 20%. In addition, the invention also provides polymer beads having a weight mean particle size in the range 0.05 to 5 mm having a standard deviation of particle size less than 20% and having an amount of residual acrylamide of less than 500 ppm. L'invention concerne un procédé de polymérisation en suspension en phase inverse destiné à la fabrication de billes de polymère, comportant la formation de billes aqueuses de monomère comprenant une solution aqueuse de monomère ou d'un mélange de monomères à insaturation éthylénique soluble(s) dans l'eau et la polymérisation du monomère ou du mélange de monomères, pour former des billes de polymère en suspension dans un liquide non aqueu