New Board Coating Method, 1998 Coating Conference Proceedings

A new board coating method has been developed to replace airknife coaters. This method consists of a free jet application of coating color, a very long color dwell time, and smooth rod metering. The free jet application of the coating color is beneficial due to a lower pressure pulse. Thus the coating color remains on the web surface, giving a good coverage. The long dwell time between application and metering gives time for capillary absorption and the development of a thick filter cake. In contrast to blade metering, rod metering gives a thicker contour coating layer. The coverage of the new method coated board equals or exceeds that of airknife coated board. In the pilot trials, smoothness was significantly better after rod coating than after airknife coating. There are benefits in gloss and brightness, too. This study suggests that, in board coating, nozzle application, a long dwell time, and rod metering give very good coverage and a smooth surface.