Improving cartonboard quality with curtain coater in WEIG KM3

The fierce competition forces paper and board producers to continuously optimize their processes and find ways to improve the quality of their products. The curtain coating technology ensures homogeneous coating layers by eliminating streaks and unevenness that typically compromise the printability and visual appeal of the board.

The curtain coater enables the application of either single or multiple extremely thin or thick uniform layers all within one coating station. The flexibility of the technology offers several advantages over conventional coating methods, while being equally suitable for both board and paper machines, regardless of the machines’ speeds and widths. The curtain coating slide die has an expandable design, allowing upgrades of the coating station by adding coating layers which gives a possibility for a wide end product assortment.

A single-layer curtain coater in the pre-coating process ensures uniform and consistent coverage, which is a critical advantage when working with recycled fiber. This approach delivers financial benefits by enabling a higher yield during fiber cleaning: the reject ratio can be decreased, and more impurities can be tolerated in the accepted fiber because the curtain effectively covers them.

Board quality remains stable because the curtain coater as a pre-coating station continuously applies the desired amount of coating in both cross and machine directions. In contrast, conventional methods require frequent adjustments to the coating amount, which inevitably leads to quality fluctuations.

Efficient boundary air removal and a fully shielded coating process ensure uniform and stable curtain coating while the contactless coating application method delivers excellent runnability and efficiency over a wide operation window. The curtain coater comes with a sophisticated coating color supply system including degasser ensuring the 100% airless coating.

In December 2024 WEIG Group started up a state-of-the-art curtain coating station on their board machine KM3 in Mayen. This investment replaced an old air knife coater and has enhanced the quality of the board by improving coating coverage and reducing streakiness of the coating. In this presentation the results from the first year of curtain coater operation are presented as well as experiences from the start-up.