Optimised Precoats for Multilayer Coating, 2011 PaperCon Conference

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In today’s fine paper and coated board markets we now believe it can make more sense to use the functionality of kaolin in precoating rather than in topcoating. While carbonates can be made fine enough to deliver gloss they cannot be modified sufficiently in shape to improve coverage . As a result, we conclude that the value of kaolin in today’s cost focussed coated fine paper market is therefore in its ability to cover the surface, not in its ability to generate paper gloss.

In this paper we show how low levels of kaolin (20-25 parts) can improve precoat coverage and evenness through pilot coater evaluations of different precoat concepts on a fine paper and board basestocks. We go on to explore the impact of precoat design on finished paper properties through a series of laboratory studies in which topcoat pigment selection and formulation was varied. We show that using optimised precoats can give more degrees of freedom for reducing kaolin and binder in the topcoat which can lead to improved quality or reduced cost in regions where imported kaolin is significantly higher in price than local carbonates.