Automating the Coating Kitchen, 1991 Coating Conference Proceedings

White Pigeon Paper Co. produces clay coated recycled paperboard using a 7 unit Ultraformer machine. During the last 25 years, it had been modernized in sections. This included a Waldron Air Knife coater. In 1986, it was time to update the coating system. This would include a rod precoater and a new-coating kitchen. It was desired to have a coating kitchen design that would provide a consistent coating from batch to batch, as well as flexibility for changes, and to have uniform coating weight. Experience had shown that coating made in the old coating kitchen was susceptible to human error and varied in binder content, solids, viscosity and brightness. An investigation led to a computer controlled system that incorporated electronic load cells, a programmable controller, automatic ingredient addition with high accuracy and automatic mixing. The incorporation of in-line, pressurized, screening helped coating uniformity. Data shows that the new coating kitchen has greatly reduced variation in solids, viscosity, brightness and binder level. Resulting clay coated board shows more consistent brightness, and printing characteristics, such as coating weight and K & N Absorption. Coating weight on the paperboard machine may vary only +3% in a 24-hour period.