Method for preventing formation of a heavy liquid layer on a web at a

Abstract

A method for coating a web with a coating liquid wherein heavy coating of the web at the coating start position with the coating liquid is prevented. While a thin layer of pretreatment liquid having a low viscosity and consisting of water and/or organic solvent is applied at the coating start position and the region around the coating start position on the web, the web is fed into a coating section where the web is coated with the coating liquid with the coating liquid applied over the thin layer of pretreatment liquid on the web. With the coating operation carried out with a hopper-type coating device, a method is preferably employed in which the amount of pressure reduction of a bead stabilizing suction chamber is set at value higher than that used for steady-state operation. The coating liquid is applied onto the thin layer of pretreatment liquid on the web and thereafter the pressure reduction is returned to that normally used for steady-state operation to continue the coating operation with the coating liquid. In this dual-layer coating operation, heavy coating of the web at the coating start position with the coating liquid is prevented by cooperation of the expansive wetting effect of the thin layer of pretreatment liquid and the higher pressure reduction of the suction chamber.