Advances in the Use of Dry Co-Binders in Coating Color Preparation, 2003 Spring Technical Conference Proceedings

Dry components have been successfully used in the coating color preparation for several years. There is nothing new about feeding and mixing dry co-binders e.g. CMC directly in the coating mixer. By adding dry components, the mills try to maximize the dry solids content of the coating color. This is very sensible while doing so the runnability, coated paper quality and last but not least the production economy is improved. In most cases all these benefits are achieved.

When one target has been achieved the organizations tend to select the next target. Often it is to increase the production capacity by increasing the speed on the paper machine. When doing so naturally the demand for fresh coating color will also increase and often the coating kitchens are pushed to their very limits. Pushing the limits often means that superintendents are forced to cut corners by ordering that e.g. several components are fed into the mixer simultaneously. By doing so you can forget all the optimized addition orders, pH stabilization and so on. The second step in increasing the kitchen capacity is to cut down on the mixing time during coating preparation. A decrease of mixing time of 5 minutes after the dry CMC addition might just give you the extra capacity you need to cope with the new requirements set by the increased paper machine speed. Does this sound familiar?

Metso PaperChem recognized the problems around dry addition of co-binders and started an extensive project to improve the situation. This paper will describe the system developed to solve the problem with dry addition of components. Research work, trials and also mill experiences will be discussed.