Method and apparatus for coating a web

摘要

A traveling web is coated on both sides with an aqueous coating composition by a method that utilizes apparatus providing two coating stations. The two coating stations are spaced from each other in the direction of travel of the web and each station includes a backing roll, a doctor blade and a device for applying coating composition to one side of the traveling web. One side of the web is brought into contact with the backing roll at the first coating station and aqueous coating composition is applied to the other side of the web. The web is then passed between the backing roll and the doctor blade at the first coating station. At the second coating station, the coated side of the web is juxtaposed with the backing roll and aqueous coating composition is applied to the uncoated side of the web. The web is passed between the backing roll and the doctor blade at the second coating station, while the doctor blade is maintained in contact with the coating composition applied at the second coating station. To prevent the coating applied at the first coating station from adhering to the backing roll at the second coating station, the surface of the backing roll at the second station is cooled so that moisture in the coating composition applied at the first coating station forms at least part of a film of condensate on the surface of the roll. The coating composition applied at the first coating station thus contacts the film of condensate, rather than the surface of the roll.