Continuously screening shear-sensitive aq. polymer dispersions - in device contg. inclined screening plane and baffle plate enclosed in housing

摘要

Aq. polymer dispersions, sensitive to shearing and contg. 10-60 wt % solids esp. with >=40 wt % polymerised vinyl chloride units, 0.01-5 wt % emulsifiers and opt. 0.01-10 wt % protective colloids, are screened in a screening device having a screening plane inclined 30-70 degrees w.r.t. horizontal. A baffle plate is situated 5-25 cm below screening plate, in a plane parallel to screening plane. The baffle plate dips at least into a liquid level. The screening plate and baffle plate are built into a closed housing, the lid interior of which is fitted with spray jets. The upper end of the screening plate is limited by a supply conduit with over-flow, and the lower end by a discharge screw conveyor for screened coarse material, on one hand, and, separately, by a filtrate collecting main. Polymer dispersions, tending to cake together and agglomerate, can be screened continuously. Environmental pollution by monomers can be minimised.