Coating moulds with mould wash - by contact of mould wash aerosol with mould across which pressure gradient is established

摘要

The mould wash, in the form of an aerosol suspension, is held in a deposition chamber, part of the wall of which is formed by the mould surface to be coated, and a pressure gradient between this mould surface and the outer surface of the mould is established to produce a gas flow from the chamber through the mould. Pref. the pressure gradient is established by applying a vacuum to the outer surface of the mould, the vacuum pref. being maintained until the mould wash coating is dry. Uniform mould wash coatings are produced rapidly and the coating dries rapidly from the inside layer to the outside layer (due to the directional flow of gas and entrained solvent vapour) so that the coating does not run. The gas permeability of the coating decreases rapidly with increasing coating thickness thus improving coating thickness uniformity even in e.g. recessed and upraised mould regions. Selective mould wash coating is possible by using gas-impermeable masks.