Process for separating polyvinyl alcohol from its solution

An apparatus for coagulating particles of dissolved solids from an aqueous solution which comprises an upright stirring vessel provided with a stirrer and a plurality of obstructing plates disposed vertically along the inner wall of said vessel, the stirrer comprising a substantially vertical shaft, a plurality of flat, radially extending blades secured symmetrically around said shaft in such a relation that both flat surfaces of each blade are substantially parallel to the plane of rotation of the blades, a plurality of knives extending upwardly and downwardly from said blades, each knife being a flat piece fixed to the top or underside surface of said blades in such a relation that each knife is approximately perpendicular to the longitudinal direction of the blade to which the knife is fixed and the flat surfaces of each knife being substantially tangential to the cylindrical plane of rotation of the knife, said obstructing plates being secured to the inner wall of the vessel so as to obstruct the swirling motion in the solution provided by the stirrer.