Curtain coating, machines

Curtain coating With this process, paint falls in a continuous curtain from a closely machined gap in a header tank on to the flat article passing below on a horizontal conveyor the excess paint is collected in the main tank and then passed up to the header tank. It is an ideal method of applying thicker coatings (60/im and above) to sheet metalwork. 

Automatic spraying, machine roller coating, and curtain coating are used for industrial application of furniture coatings. Drying is accelerated by air circulation and/or increased temperature up to 80 C. IR drying ovens and tunnels are also used. 

A rather elaborate machine is required to perform this process. The glass plates and lenses are supported on a heated horizontal rotating disk having a maximum speed of 60 r-p-m. Burners or gas-mixer nozzles are supported and geared to sweep back and forth horizontally across the work pieces, one depositing 2, and the other SiC>2. Mixed oxides can be formed by the simultaneous operation of two nozzles so that 2 and SiC>2 are deposited alternately in very thin films. The titanium dioxide nozzle has two inlets for dry air, one for a mixture of dry air and titanium tetrachloride vapour and one for moist air. To prevent chemical reaction of TiCU with humid air inside the nozzle a concentric curtain of dry air between these two reaction partners is maintained. The glasses to be coated are exposed to a temperature of about 250°C and the mixture from the burner reacts on the heated surface to form 2 film... 

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